Method for forming element isolating region

Claim 1

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to then conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove said silicon nitride film and said first silicon oxide film; and removing by wet etching said pad oxide film and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 2

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to then conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove said silicon nitride film and said first silicon oxide film; and removing by wet etching said pad oxide film and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 5

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove each part of said silicon nitride film and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching a residue of said second silicon oxide film, said thermal-oxidized film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 6

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove each part of said silicon nitride film and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching a residue of said second silicon oxide film, said thermal-oxidized film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 9

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove each part of said silicon nitride film and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said pad oxide film and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 10

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove each part of said silicon nitride film and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said pad oxide film and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 13

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase a second silicon oxide film which covers said silicon nitride film and said first silicon oxide film to thereby conduct heat treatment, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be higher than an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove a part of said silicon nitride film at the same time as removing said first silicon oxide film until a surface of said first silicon oxide film is equal to a surface of said pad oxide film in level; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said second oxide film, said pad oxide film and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 14

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film throughout on said surface of said silicon substrate by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase a second silicon oxide film which covers said silicon nitride film and said first silicon oxide film to thereby conduct heat treatment, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be higher than an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove a part of said silicon nitride film at the same time as removing said first silicon oxide film until a surface of said first silicon oxide film is equal to a surface of said pad oxide film in level; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said second oxide film, said pad oxide film and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 17

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film which has a film thickness smaller than one-half of a minimum width of said trenches by low pressure chemical vapor deposition throughout on said surface of said silicon substrate; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film silicon oxide films to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film until said silicon nitride film is removed completely; and removing by wet etching said pad oxide film, said second silicon oxide film, and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 18

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film which has a film thickness smaller than one-half of a minimum width of said trenches by low pressure chemical vapor deposition throughout on said surface of said silicon substrate; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film silicon oxide films to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film until said silicon nitride film is removed completely; and removing by wet etching said pad oxide film, said second silicon oxide film, and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 20

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical deposition on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film to thereby conduct second heat treatment, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film so as to leave a part of said silicon nitride film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching a residue of said third silicon oxide film, said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 21

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical deposition on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film to thereby conduct second heat treatment, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film so as to leave a part of said silicon nitride film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching a residue of said third silicon oxide film, said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 23

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers surfaces of said silicon nitride film and said first silicon oxide film and second silicon oxide film to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting anisotropic etching using such an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be higher than an etching rate for said silicon nitride film to remove said third silicon oxide film, thus removing each part of said silicon nitride film, said second silicon oxide film, and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 24

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers surfaces of said silicon nitride film and said first silicon oxide film and second silicon oxide film to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting anisotropic etching using such an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be higher than an etching rate for said silicon nitride film to remove said third silicon oxide film, thus removing each part of said silicon nitride film, said second silicon oxide film, and said first silicon oxide film; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 26

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct a first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers surfaces of said silicon nitride film and said first silicon oxide film and said second silicon oxide film to thereby conduct a second heat treatment, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be higher than an etching rate for said silicon nitride film to remove said third silicon oxide film and remove a part of said silicon nitride film and also remove said second silicon oxide film and said first silicon oxide film until a surface of said second silicon oxide film and an upper edge surface of said first silicon oxide film is equal to a surface of said pad oxide film in level; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said third oxide film, said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 27

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, thus forming a first silicon oxide film having a film thickness smaller than one-half of a minimum width of said trenches throughout on said surface of said silicon substrate by low pressure chemical vapor deposition; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct a first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers surfaces of said silicon nitride film and said first silicon oxide film and said second silicon oxide film to thereby conduct a second heat treatment, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be higher than an etching rate for said silicon nitride film to remove said third silicon oxide film and remove a part of said silicon nitride film and also remove said second silicon oxide film and said first silicon oxide film until a surface of said second silicon oxide film and an upper edge surface of said first silicon oxide film is equal to a surface of said pad oxide film in level; removing a residue of said silicon nitride film by wet etching; and removing by wet etching said third oxide film, said pad oxide film, said second silicon oxide film, and said first silicon oxide film until said surface of said silicon substrate is exposed.

Claim 29

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to then conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, then forming a thermal-oxidized film on said surface of said silicon substrate including surfaces of said trenches, thus forming a first silicon oxide film throughout on said surface by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove said silicon nitride film and said first silicon oxide film; and removing by wet etching said pad oxide film, said thermal-oxidized film and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 30

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to then conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, then forming a thermal-oxidized film on said surface of said silicon substrate including surfaces of said trenches, thus forming a first silicon oxide film throughout on said surface by high-density plasma-enhanced chemical vapor deposition; conducting chemical mechanical polishing on said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers said surface of said silicon nitride film and a surface of said first silicon oxide film to thereby conduct heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film and said second silicon oxide film may be equal to an etching rate for said silicon nitride film to thereby remove said second silicon oxide film in order to remove said silicon nitride film and said first silicon oxide film; and removing by wet etching said pad oxide film, said thermal-oxidized film and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 31

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, then forming a thermal-oxidized film on said surface of said silicon substrate including surfaces of said trenches, thus forming a first silicon oxide film which has a film thickness smaller than one-half of a minimum width of said trenches by low pressure chemical vapor deposition throughout on said surface of said silicon substrate; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film silicon oxide films to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film until said silicon nitride film is removed completely; and removing by wet etching said pad oxide film, said thermal-oxidized film, said second silicon oxide film, and said first silicon oxide film until at least said surface of said silicon substrate is exposed.

Claim 32

A method for forming an element isolating region, comprising steps of: forming a pad oxide film on a surface of a silicon substrate by thermal oxidation and forming a silicon nitride film which covers said pad oxide film and then conducting anisotropic etching sequentially on portions of said silicon nitride film and said pad oxide film which exist on a formation-reserved element isolating region to conduct anisotropic etching using said silicon nitride film as a mask in order to form trenches in said surface of said silicon substrate, then forming a thermal-oxidized film on said surface of said silicon substrate including surfaces of said trenches, thus forming a first silicon oxide film which has a film thickness smaller than one-half of a minimum width of said trenches by low pressure chemical vapor deposition throughout on said surface of said silicon substrate; forming by spin coating or liquid-phase deposition a second silicon oxide film which covers a surface of said first silicon oxide film to thereby conduct first heat treatment in an oxygen atmosphere, serving also to refine said second silicon oxide film; conducting chemical mechanical polishing on said second silicon oxide film and said first silicon oxide film until a surface of said silicon nitride film is exposed; forming by spin coating or liquid-phase deposition a third silicon oxide film which covers said silicon nitride film and said first silicon oxide film and said second silicon oxide film silicon oxide films to thereby conduct second heat treatment in an oxygen atmosphere, serving also to refine said third silicon oxide film; conducting such anisotropic etching using an etching gas that an etching rate for said first silicon oxide film, said second silicon oxide film and said third silicon oxide film may be equal to an etching rate for said silicon nitride film to remove said third silicon oxide film and also remove said silicon nitride film, said second silicon oxide film, and said first silicon oxide film until said silicon nitride film is removed completely; and removing by wet etching said pad oxide film, said thermal-oxidized film, said second silicon oxide film, and said first silicon oxide film until at least said surface of said silicon substrate is exposed.