Abstract Disclosed is a device isolating method of a semiconductor device, comprising the steps of sequentially forming a pad oxide film, a polysilicon film and an insulating layer, on a silicon substrate, said insulating layer being composed of a first silicon oxide film, a nitride film and a second silicon oxide film formed sequentially on the polysilicon film; defining active and inactive regions by using a patterned photomask; removing the insulating layer only on the inactive region so as to expose a surface of the polysilicon film; forming a side wall at both edges of the insulating layer on the active region, said side wall being composed of a nitride film; depositing a third silicon oxide film on the surface of the polysilicon film; removing the side wall and etching the substrate to a predetermined depth to form a trench; filling an insulating material into the trench and depositing it up to the second silicon oxide so as to form an insulating film for isolating; simultaneously removing the second silicon oxide film and the silicon oxide film and removing the polysilicon film only the inactive region; performing a thermal oxidation to form a field oxide film on the inactive region; and sequentially removing the isolating layer and the polysilicon film formed on the active region. Because the active region is defined using an insulator-filled shallow trench before performing thermal oxidation, no oxygen is penetrated into the active region during the thermal oxidation, whereby a field oxide film can be formed without occurrence of a Bird's beak.
A method for fabricating a semiconductor device, the method comprising the steps of: sequentially forming a pad oxide film, a first polysilicon film, a silicon oxide film, a nitride film and a second polysilicon film, on a silicon substrate; defining active and inactive regions by using a trench mask and forming a trench at both sides of the active region by etching; depositing an insulating material in the trench and on the remaining portion of the second polysilicon film such that the trench is filled to form an insulating film for isolating; polishing the insulating film using the remaining portion of the second polysilicon film as a first polishing stopper; removing the remaining portion of the second polysilicon film and polishing the insulating film using the remaining portion of the nitride film as a second polishing stopper; removing the remaining portion of the nitride film and the remaining portion of the silicon oxide film; depositing and patterning a protective insulating film such that it remains only on the active region; removing the resulting exposed portion of the remaining portion of the first polysilicon film to expose a surface of the pad oxide film; performing a thermal oxidation to form a field oxide film only at the inactive region; and removing the films formed on the pad oxide film of the active region.
Claim 2
Independent Claim
222 words
A method for fabricating a semiconductor device, the method comprising the steps of: sequentially forming a pad oxide film, a first polysilicon film, a silicon oxide film, a nitride film and a second polysilicon film, on a silicon substrate; defining active and inactive regions by using a trench mask and forming a trench at both sides of the active region by etching; depositing an insulating material in the trench and on the remaining portion of the second polysilicon film such that the trench is filled to form an insulating film for isolating; polishing the insulating film using the remaining portion of the second polysilicon film as a first polishing stopper; removing the remaining portion of the second polysilicon film and polishing the insulating film using the remaining portion of the nitride film as a second polishing stopper; removing the remaining portion of the nitride film and the remaining portion of the silicon oxide film; depositing and patterning a protective insulating film such that it remains only on the active region; removing the resulting exposed portion of the remaining portion of the first polysilicon film to expose a surface of the pad oxide film; performing a thermal oxidation to form a field oxide film only at the inactive region; and removing the films formed on the pad oxide film of the active region.
Claim 3
Dependent Claim
36 words
The method as defined in claim 1, wherein the depth of the trench is set in the range of 5 μm or less, and the width of the trench is set at 3 μm or less.
Claim 4
Dependent Claim
34 words
The method as defined in claim 1, wherein the first polysilicon film has a thickness of about 2000 Å and the pad oxide film has a thickness of from 300 Å to 500 Å.
Claim 5
Dependent Claim
25 words
The method as defined in claim 1, wherein the insulating material filled in the trench is formed of one of BPSG, silicon nitride and polyimide.