Semiconductor device having dielectric isolation region of U-groove structure and process for fabricating the same

Claim 2

A semiconductor device defined in claim 1, wherein said semiconductor substrate includes a p-type silicon body, an n⁺ buried layer over the surface of said silicon body and an n-type silicon epitaxial layer formed over the surface of said buried layer; and said U-groove extends through said epitaxial layer and said buried layer.

Claim 3

A semiconductor device defined in claim 2, wherein said insulating film is composed of a silicon oxide film formed by heat oxidation and a silicon nitride film formed by the gas phase growth process.

Claim 4

A semiconductor device defined in claim 1, wherein the surface of said U-groove polysilicon is at a level lower than the upper edge of said U-groove, and a SOG film is contained in the recess defined by said silicon nitride film directly covering the surface of said U-groove polysilicon.

Claim 5

A semiconductor device defined in claim 4, wherein said semiconductor substrate includes a p-type silicon substrate, an n⁺ buried layer over the surface of said silicon substrate, and an n-type silicon epitaxial layer over the surface of said buried layer; and said U-groove extends through said silicon epitaxial layer and said buried layer.

Claim 6

A semiconductor device defined in claim 5, wherein said insulating film is composed of a silicon oxide film formed by heat oxidation and a silicon nitride film formed by the vapor phase growth process.

Claim 7

A process of fabricating a semiconductor device comprising a series of steps for forming a first insulating film on a major surface of a silicon substrate; forming a U-groove on said semiconductor substrate with said first insulating film as a mask; forming a second insulating film over the inner surface of said U-groove; forming a third insulating film covering said first and second insulating films; filling with polysilicon said U-groove having said second and third insulating films over the inner surface thereof; removing the exposed portions of said third insulating film using said polysilicon as a mask; and forming a silicon nitride film covering the surface of said polysilicon.

Claim 8

A process of fabricating semiconductor device defined in claim 7, wherein said first insulating film is a silicon oxide film formed by thermal oxidation of a major surface of said silicon substrate; said second insulating film is a silicon oxide film formed by thermal oxidation of the inner surface of said U-groove; and said third insulating film is a silicon nitride film formed by the vapor phase growth process.

Claim 9

A process of fabricating a semiconductor device defined in claim 8, wherein said U-groove is filled with polysilicon to a level lower than the upper edge of said U-groove; a SOG film is coated over the surface of said silicon film covering the surface of said U-groove polysilicon and sintered; and the recess defined by said silicon film covering the surface of the U-groove polysilicon is filed with said SOG film.

Claim 10

A process of fabricating a semiconductor device comprising a series of steps for forming an n⁺ buried layer on a major plane of a p-type silicon substrate, forming an n-type silicon epitaxial layer over the surface of said n⁺ buried layer, forming a first insulating film over said silicon epitaxial layer; forming a U-groove extending through said silicon epitaxial layer and said buried layer using said first insulating film as a mask; forming a second insulating film over the inner surface of said U-groove; forming a third insulating film covering said first and second insulating films; filling with polysilicon said U-groove having said second and third insulating films over the inner surface thereof; removing exposed portions of said third insulating film using said U-groove polysilicon as a mask; and forming a silicon nitride film covering the surface of said U-groove polysilicon.

Claim 11

A process of fabricating a semiconductor device defined in claim 10 wherein said first insulating film is a silicon oxide film formed by thermal oxidation of the surface of said epitaxial layer; said second insulating film is a silicon oxide film formed by thermal oxidation of the inner surface of said U-groove; and said third insulating film is a silicon nitride film formed by the vapor phase growth technique.

Claim 12

A process of fabricating a semiconductor device defined in claim 11 wherein said U-groove is filled with polysilicon to a level lower than the upper edge of said U-groove; a SOG film is coated over the surface of said silicon covering the surface of said U-groove polysilicon and sintered; and the recess defined by said silicon film covering said the surface of said U-groove polysilicon is filled with said SOG film.