Semiconductor device and method for facticating the same

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

• a) forming a gate insulating film and a gate electrode in this order on a semiconductor layer in a substrate;
• b) depositing a silicon dioxide film and a silicon nitride film in this order over the substrate, and then anisotropically etching back the silicon dioxide film and the silicon nitride film, thereby forming a nitride sidewall and a stress-relaxing oxide film that surround the gate electrode, the stress-relaxing oxide film being interposed between the gate electrode and the nitride sidewall and between the semiconductor layer and the nitride sidewall film so as to have an L-shaped cross section;
• c) nitriding a lower edge of the stress-relaxing oxide film, thereby changing the lower edge into an oxynitride region;
• d) defining source/drain regions in parts of the semiconductor layer below the gate electrode to horizontally sandwich the gate electrode therebetween;
• and
• e) siliciding respective uppermost parts of the source/drain regions.

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

• a) forming a gate insulating film and a gate electrode in this order on a semiconductor layer in a substrate;
• b) forming a stress-relaxing insulator sidewall around the gate electrode;
• c) depositing a silicon nitride film over the substrate;
• d) depositing an antireactive oxide film over the silicon nitride film;
• e) selectively removing part of the antireactive oxide film located in a region to be silicided while leaving the other part of the antireactive oxide film located in a region not to be silicided;
• f) anisotropically etching part of the silicon nitride film located in the region to be silicided, thereby forming a nitride sidewall on the insulator sidewall so that the nitride sidewall is in contact with the semiconductor layer;
• g) defining source/drain regions in parts of the semiconductor layer below the gate electrode to horizontally sandwich the gate electrode therebetween;
• and
• h) siliciding respective uppermost parts of the source/drain regions.