Spacer structure wherein carbon-containing oxide film formed within

1. A spacer structure comprising:

a nitride film positioned on a gate sidewall;

a first carbon-containing oxide film disposed between the gate sidewall and the nitride film; and

a second carbon-containing oxide film covering the nitride film, and the nitride film being disposed between the first carbon-containing oxide film and the second carbon-containing oxide film.

2. The spacer structure of claim 1 , wherein the first carbon-containing oxide film and the nitride film together compose an L-shaped structure.

3. The spacer structure of claim 1 , wherein the nitride film is a carbon-containing nitride film.

4. The spacer structure of claim 1 , wherein the spacer structure further comprises an offset spacer positioned between the gate sidewall and the first carbon-containing oxide film.

5. The spacer structure of claim 4 , wherein the offset spacer comprises an oxide film.

6. The spacer structure of claim 5 , wherein the oxide film of the offset spacer is a third carbon-containing oxide film.

7. The spacer structure of claim 5 , wherein the offset spacer further comprises a nitride film between the oxide film of the offset spacer and the first carbon-containing oxide film.

8. The spacer structure of claim 7 , wherein the nitride film is a carbon-containing nitride film.

9. The spacer structure of claim 1 , wherein the first carbon-containing oxide film and the nitride film respectively have an L-shaped profile.

10. The spacer structure of claim 1 , wherein the nitride film directly contacts and directly covers a surface of the first carbon-containing oxide film, and the surface of the first carbon-containing oxide film is in parallel with the gate sidewall.

11. A metal-oxide-semiconductor (MOS) transistor structure comprising:

a gate electrode positioned on a substrate;

a source and drain positioned in the substrate near two sides of the gate electrode;

a gate insulation film positioned between the gate electrode and the silicon substrate; and

a spacer structure positioned on the sidewall of the gate electrode, the spacer structure comprising:

an offset spacer positioned on the sidewall of the gate electrode; and

an L-shaped structure covering the offset spacer comprising:

a nitride film covering the surface of the offset spacer;

a first carbon-containing oxide film disposed between the surface of the offset spacer and the nitride film; and

a second carbon-containing oxide film covering the nitride film, and the nitride film being disposed between the first carbon-containing oxide film and the second carbon-containing oxide film.

12. The MOS transistor structure of claim 11 , wherein the nitride film is a carbon-containing nitride film.

13. The MOS transistor structure of claim 11 , wherein the offset spacer comprises an oxide film.

14. The MOS transistor structure of claim 13 , wherein the oxide film of the offset spacer is a third carbon-containing oxide film.

15. The MOS transistor structure of claim 13 , wherein the oxide film of the offset spacer covers the sidewall of the gate electrode.

16. The MOS transistor structure of claim 13 , wherein the offset spacer further comprises a nitride film between the oxide film of the offset spacer and the first carbon-containing oxide film.

17. The MOS transistor structure of claim 16 , wherein the nitride film is a carbon-containing nitride film.

18. The MOS transistor structure of claim 11 , wherein each of the first carbon-containing oxide film and the nitride film has an L-shaped profile.

19. The MOS transistor structure of claim 11 , wherein the nitride film directly contacts and directly covers a surface of the first carbon-containing oxide film, and the surface of the first carbon-containing oxide film is in parallel with the sidewall of the gate electrode.

20. The MOS transistor structure of claim 11 , wherein the nitride film is disposed on the two sides of the gate electrode without covering a top surface of the gate electrode.