Semiconductor device and method for fabricating the same

1 . A semiconductor device comprising:

an isolation region formed in a semiconductor substrate;

an active region surrounded by the isolation region of the semiconductor substrate;

a fully silicided first gate line formed on the active region;

a fully silicided second gate line formed on the isolation region;

a first sidewall formed on a side of the first gate line;

a second sidewall formed on a side of the second gate line,

the length between the top and bottom surfaces of the first sidewall being different from that between the top and bottom surfaces of the second sidewall.

2 . The semiconductor device of claim 1 , wherein

the top surface of the isolation region located below the second gate line is above the top surface of the active region, and

the length between the top and bottom surfaces of the first sidewall is larger than that between the top and bottom surfaces of the second sidewall.

3 . The semiconductor device of claim 1 , wherein

the top surface of the first sidewall is at the same level as the top surface of the second sidewall.

4 . The semiconductor device of claim 1 , wherein

the top surface of the first sidewall is unflat, and the top surface of the second sidewall is flat.

5 . The semiconductor device of claim 1 , wherein

the top surfaces of the first and second sidewalls are flat.

6 . The semiconductor device of claim 1 , wherein

the first and second gate lines have the same composition.

7 . The semiconductor device of claim 1 , wherein

the first and second gate lines have different compositions.

8 . The semiconductor device of claim 1 further comprising

a gate insulating film formed between the active region and the first gate line,

the first gate line functioning as a gate electrode.

9 . The semiconductor device of claim 8 , wherein

the gate insulating film is a high-dielectric-constant film having a dielectric constant of 10 or more.

10 . The semiconductor device of claim 8 , wherein

the gate insulating film is a film containing a metal oxide.

11 . The semiconductor device of claim 1 further comprising

impurity diffusion layers formed in regions of the active region located to both sides of the first gate line.

12 . A method for fabricating a semiconductor device, said method comprising the steps of:

(a) forming an active region and an isolation region in a semiconductor substrate, said isolation region surrounding the active region;

(b) forming a first gate including a first gate formation silicon film on the active region and forming a second gate including a second gate formation silicon film on the isolation region;

(c) forming an insulating film covering the first and second gates;

(d) partially polishing away the insulating film and the second gate by CMP to expose at least the top surface of the first gate;

(e) after the step (d), forming a metal film to cover the semiconductor substrate, the first gate formation silicon film of the first gate and the second gate formation silicon film of the second gate, and then subjecting the metal film to heat treatment to fully silicide the first and second gate formation silicon films, thereby forming first and second gate lines on the active region and the isolation region, respectively.

13 . The method of claim 12 , wherein

in the step (a), the top surface of the isolation region is located above the top surface of the active region.

14 . The method of claim 12 further comprising the step of

(f) between the steps (a) and (b), forming a gate insulating film on the active region,

the first gate line on the gate insulating film functioning as a gate electrode.

15 . The method of claim 12 further comprising the step of

(g) between the steps (b) and (c), forming a first sidewall on a side of the first gate and forming a second sidewall on a side of the second gate,

wherein the step (d) includes the sub-step of partially polishing away the second sidewall by CMP, and

after the step (d), the length between the top and bottom surfaces of the first sidewall is larger than that between the top and bottom surfaces of the second sidewall.

16 . The method of claim 12 , wherein

the insulating film is an underlayer insulating film formed below an interlayer dielectric.

17 . The method of claim 12 , wherein

the insulating film includes an underlayer insulating film and an interlayer dielectric covering the underlayer insulating film.

18 . The method of claim 16 , wherein

the underlayer insulating film is a silicon nitride film, a silicon oxynitride film, or a stress-applying insulating film having a stress.

19 . The method of claim 12 , wherein

the step (b) includes the sub-steps of sequentially forming a gate formation silicon film and a protective film to cover the active region and the isolation region, and patterning the gate formation silicon film and the protective film into the first gate including the first gate formation silicon film and a first protective film and the second gate including the second gate formation silicon film and a second protective film,

the step (d) includes the sub-step of partially polishing away the insulating film and the second protective film of the second gate by CMP until the top surface of the first protective film of the first gate is exposed, and

the method further comprises the step of (h) between the steps (d) and (e), removing the first protective film and the remaining part of the second protective film.

20 . The method of claim 12 , wherein

the step (b) includes the sub-steps of sequentially forming a gate formation silicon film and a protective film to cover the active region and the isolation region, and patterning the gate formation silicon film and the protective film into the first gate including the first gate formation silicon film and a first protective film and the second gate including the second gate formation silicon film and a second protective film,

the step (d) includes the sub-step of polishing away part of the insulating film, part of the first protective film of the first gate and the second protective film of the second gate by CMP until the top surface of the second gate formation silicon film of the second gate is exposed, and

the method further comprises the step of (h) between the steps (d) and (e), removing the remaining part of the first protective film.

21 . The method of claim 12 , wherein

the step (b) includes the sub-steps of sequentially forming a gate formation silicon film and a protective film to cover the active region and the isolation region, and patterning the gate formation silicon film and the protective film into the first gate including the first gate formation silicon film and a first protective film and the second gate including the second gate formation silicon film and a second protective film, and

the step (d) includes the sub-step of polishing away part of the insulating film, the first protective film of the first gate, the second protective film of the second gate, and part of the second gate formation silicon film by CMP until the top surface of the first gate formation silicon film of the first gate is exposed.

22 . The method of claim 12 , wherein

the step (b) includes the sub-steps of forming a gate formation silicon film to cover the active region and the isolation region, and patterning the gate formation silicon film into the first gate including the first gate formation silicon film and the second gate including the second gate formation silicon film, and

the step (d) includes the sub-step of polishing away part of the second gate formation silicon film of the second gate by CMP until the top surface of the first gate formation silicon film of the first gate is exposed.