Semiconductor device and method for fabricating the same

1. A semiconductor device comprising:

an n-type MIS transistor formed on a first active region of a semiconductor substrate and including a first gate electrode formed on the first active region and a first sidewall formed on a side face of the first gate electrode; and

a p-type MIS transistor formed on a second active region of the semiconductor substrate and including a second gate electrode formed on the second active region, a second sidewall formed on a side face of the second gate electrode and having a smaller thickness along a gate length direction than the first sidewall, and silicon germanium layers formed in the second active region in portions of the second active region disposed outside the second sidewall,

wherein the number of layers included in the first sidewall is equal to the number of layers included in the second sidewall.

2. The semiconductor device of claim 1 ,

wherein the second active region has recesses disposed outside the second gate electrode, and

the silicon germanium layers are filled in the recesses.

3. The semiconductor device of claim 1 , wherein each of the first sidewall and the second sidewall includes a first insulating film having an L-shaped cross-section and a second insulating film formed over the first insulating film.

4. The semiconductor device of claim 1 ,

wherein the n-type MIS transistor further includes n-type extension diffusion layers formed in portions of the first active region disposed on both sides of the first gate electrode, and n-type source/drain regions formed in portions of the first active region disposed outside the first sidewall,

the p-type MIS transistor further includes p-type extension diffusion layers formed in portions of the second active region disposed on both sides of the second gate electrode, and

the silicon germanium layers are formed outside the p-type extension diffusion layers farther from the channel region and have a larger depth than the p-type extension diffusion layers.

5. The device of claim 1 , wherein a highest part of an upper surface of each of the silicon germanium layers is higher than a surface of a region of the second active region located directly under the second gate electrode.

6. The device of claim 3 , wherein

the first insulating film is made of silicon oxide, and

the second insulating film is made of silicon nitride.

7. The device of claim 1 , wherein each of the first gate electrode and the second gate electrode is made of polysilicon.

8. The device of claim 1 , wherein each of the first active region and the second active region is surrounded by an isolation region formed in the semiconductor substrate.

9. The device of claim 1 , wherein

the first gate electrode is formed on the first active region with a first gate insulating film interposed therebetween,

the second gate electrode is formed on the second active region with a second gate insulating film interposed therebetween, and

the first gate insulating film and the second gate insulating film are made of a silicon oxide film, a silicon oxy-nitride film, or a silicon nitride film.

10. The device of claim 1 , wherein the silicon germanium layers are made of an epitaxial layer.

11. The device of claim 1 , wherein the silicon germanium layers applies compressive stress along the gate length direction to a channel region of the p-type MIS transistor.

12. The device of claim 1 , wherein

the first sidewall includes a first insulating film having an L-shaped cross-section and formed on the side face of the first gate electrode, and a second insulating film formed over the first insulating film,

the second sidewall includes a third insulating film having an L-shaped cross-section and formed on the side face of the second gate electrode, and a fourth insulating film formed over the third insulating film, and

a largest width of the fourth insulating film in the gate length direction is smaller than a largest width of the second insulating film in the gate length direction.

13. The device of claim 12 , wherein the first insulating film and the third insulating film have the same thickness.

14. The device of claim 1 , wherein a liner insulating film made of a silicon nitride film is formed on the first active region.

15. The device of claim 1 , wherein a silicon nitride film for applying tensile stress along the gate length direction to a channel region of the n-type MIS transistor is formed on the first active region.

16. The device of claim 2 , wherein a silicon nitride film for applying tensile stress along the gate length direction to a channel region of the n-type MIS transistor is formed on the first active region.

17. The device of claim 1 , wherein an edge of each of the silicon germanium layers adjoining the second sidewall is above a surface of a part of the second active region located directly under the second sidewall.

18. The device of claim 1 , wherein an edge of each of the silicon germanium layers adjoining the second sidewall is above an intersecting line at which the second active region, the second sidewall, and each of the silicon germanium layers intersect with one another.

19. The device of claim 2 , wherein an edge of each of the silicon germanium layers adjoining the second sidewall is above an intersecting line at which the second active region, the second sidewall, and each of the silicon germanium layers intersect with one another.

20. The device of claims 1 , wherein the second sidewall has a smaller thickness along the gate length direction at an intermediate in a height direction than the first sidewall.