Fabrication method and device structure of shallow trench insulation for silicon wafer containing silicon-germanium

1. A method of fabricating a semiconductor device, the method comprising:

forming a first single crystal silicon layer on a semiconductor substrate containing a single crystal silicon-germanium layer on the surface;

forming a first thermal oxide layer on the surface of said first single crystal silicon layer;

forming a silicon nitride layer on said first thermal oxide layer;

forming a trench region to a depth extending into said single crystal silicon-germanium layer on a multi layer structure made from said single crystal silicon-germanium layer, said first single crystal silicon layer, said first thermal oxide layer, and said silicon nitride layer;

forming a second single crystal silicon layer inside said trench region;

forming a second thermal oxide layer on the surface of said second single crystal silicon layer;

embedding an insulator inside said trench region, thereby forming a device isolation region; and

forming a device in an active region separated by said device isolation region,

wherein the step of forming said device in said active region includes forming a doped region of a depth to reach within said single crystal silicon-germanium layer below said first single crystal silicon layer, and

wherein the step of forming said second single crystal silicon layer includes using selective epitaxial growth.

2. The method of fabricating a semiconductor device according to claim 1 , wherein said insulator embedded inside said trench region is a silicon dioxide layer deposited over the entire surface.

3. The method of fabricating a semiconductor device according to claim 1 , wherein said semiconductor substrate is a single crystal silicon wafer, and wherein said single crystal silicon-germanium layer is a graded profile layer epitaxially formed from said single crystal silicon wafer towards the surface with a varied germanium ratio.

4. The method of fabricating a semiconductor device according to claim 1 , wherein the step of embedding an insulator comprises:

leveling the insulator material by chemical-mechanical polishing, using said silicon nitride layer on said active region as a mechanical stopper;

removing said silicon nitride layer; and

removing said first thermal oxide layer.

5. The method of fabricating a semiconductor device according to claim 1 , wherein the step of forming said device in said active region further comprises:

forming well regions on said active region;

forming a gate dielectric layer on said first single crystal silicon layer;

forming gate polycrystalline silicon on said gate dielectric layer;

forming a gate side wall structure; and

forming source drain regions.

6. A method of fabricating a semiconductor device, the method comprising:

preparing a semiconductor substrate having a single crystal silicon-germanium layer and a first single crystal silicon layer formed on said single crystal silicon-germanium layer;

forming a first silicon oxide layer on the surface of said first single crystal silicon layer;

forming a silicon nitride layer on said first silicon oxide layer;

forming a trench region to a depth extending into said single crystal silicon-germanium layer on a multi-layer structure made from said single crystal silicon-germanium layer, said first single crystal silicon layer, said first silicon oxide layer, and said silicon nitride layer;

forming a second single crystal silicon layer inside trench region and a polycrystalline layer on a side wall of said silicon nitride layer;

forming a second silicon oxide layer on said second single crystal silicon layer and said polycrystalline layer;

forming a third silicon oxide layer inside said trench region and over said silicon nitride layer;

leveling said third silicon oxide layer by chemical-mechanical polishing, using said silicon nitride layer as a mechanical stopper as said polycrystalline layer remains, thereby forming a device isolation region;

removing said silicon nitride layer;

oxidizing said polycrystalline layer after the step of leveling said third silicon oxide layer; and

forming a device in an active region separated by said device isolation region,

wherein the step of forming said device in said active region includes forming a doped region of a depth to reach within said single crystal silicon-germanium layer below said first single crystal silicon layer.

7. The method of fabricating a semiconductor device according to claim 6 , further comprising removing a fourth silicon oxide layer formed in the step of oxidizing said polycrystalline layer.

8. The method of fabricating a semiconductor device according to claim 6 , further comprising removing a part of said second silicon oxide layer, wherein the step of removing a part of said second silicon oxide layer includes removing a fourth silicon oxide layer formed in the step of oxidizing said polycrystalline layer.

9. The method of fabricating a semiconductor device according to claim 6 , wherein the step of oxidizing said polycrystalline layer is executed before the step of removing said silicon nitride layer.

10. The method of fabricating a semiconductor device according to claim 6 , wherein the step of preparing said semiconductor substrate includes the step of forming said first single crystal silicon layer on said single crystal silicon-germanium layer.

11. The method of fabricating a semiconductor device according to claim 6 , wherein the step of forming said second single crystal silicon layer and said polycrystalline layer is executed by epitaxial growth.

12. The method of fabricating a semiconductor device according to claim 6 , wherein said first silicon oxide layer is a thermal oxide layer.

13. The method of fabricating a semiconductor device according to claim 6 , wherein said second silicon oxide layer is a thermal oxide layer.

14. The method of fabricating a semiconductor device according to claim 6 , wherein the step of forming said device further comprises:

forming well regions on said active region;

forming a gate dielectric layer on said first single crystal silicon layer;

forming gate polycrystalline silicon on said gate dielectric layer;

forming a gate side wall structure; and

forming source drain regions.

15. A method of fabricating a semiconductor device, the method comprising:

preparing a semiconductor substrate having a single crystal silicon-germanium layer and a first single crystal silicon layer formed on said single crystal silicon-germanium layer;

forming a first silicon oxide layer on the surface of said first single crystal silicon layer;

forming a silicon nitride layer on said first silicon oxide layer;

forming a trench region to a depth extending into said single crystal silicon-germanium layer on a multi-layer structure made from said single crystal silicon-germanium layer, said first single crystal silicon layer, said first silicon oxide layer, and said silicon nitride layer;

forming a second single crystal silicon layer inside said trench region by selective epitaxial growth;

forming a second silicon oxide layer on said second single crystal silicon layer;

forming a third silicon oxide layer inside said trench region and over said silicon nitride layer;

leveling said third silicon oxide layer by chemical-mechanical polishing, using said silicon nitride layer as a mechanical stopper, thereby forming a device isolation region;

removing said silicon nitride layer; and

forming a device in an active region separated by said device isolation region,

wherein the step of forming said device in said active region includes forming a doped region of a depth to reach within said single crystal silicon-germanium layer below said first single crystal silicon layer.

16. The method of fabricating a semiconductor device according to claim 15 , wherein the step of preparing said semiconductor substrate includes the step of forming said first single crystal silicon layer on said single crystal silicon-germanium layer.

17. The method of fabricating a semiconductor device according to claim 15 , wherein said first silicon oxide layer is a thermal oxide layer.

18. The method of fabricating a semiconductor device according to claim 15 , wherein said second silicon oxide layer is a thermal oxide layer.

19. The method of fabricating a semiconductor device according to claim 15 , wherein the step of forming said device further comprises:

forming well regions on said active region;

forming a gate dielectric layer on said first single crystal silicon layer;

forming gate polycrystalline silicon on said gate dielectric layer;

forming a gate side wall structure; and

forming source drain regions.