Patent ID: 8168482

Claim:
A method for manufacturing a semiconductor device comprising: preparing a base made of a semiconductor material; forming a silicon oxide film including either hydrogen or deuterium on the base; diffusing nitrogen into the silicon oxide film to thereby form a gate insulating film comprising silicon oxide including the nitrogen and either the hydrogen or deuterium; forming a gate electrode on the gate insulating film; carrying out ion doping in the base such that a source region and a drain region are formed at both sides of a channel region of the base which is in contact with the gate electrode through the gate insulating film; and forming a source electrode electrically connecting to the source region of the base and a drain electrode electrically connecting to the drain region of the base to thereby obtain the semiconductor device; wherein by diffusing the nitrogen into the silicon oxide film in the diffusing step, the amount of either the hydrogen or deuterium residing in the vicinity of an interface between the formed gate insulating film and the base is relatively reduced so that the gate insulating film has a first region where B/A is in the range of 1.6 to 8.6, where a concentration of the nitrogen in the region being defined as A, and a concentration of the hydrogen or the deuterium in the region being defined as B, and wherein the first region is located at a portion of the gate insulating film at a first distance toward a thickness direction of Y/10 of the gate insulating film from the interface, where Y is an average thickness of the gate insulating film, and wherein the gate insulating film has a second region where the B/A is in the range of 10.3 to 16.3, and the second region is located at a portion of the gate insulating film at a second distance toward the thickness direction of Y/3 of the gate insulating film from the interface.