Semiconductor device having sidewall portion with silicon nitride film formed above layer and separated from region above primary insulating film via oxide film, where the portion is formed on sidewall of gate electrode

A semiconductor device, comprising:

• a semiconductor layer;
• a first insulating film formed in said semiconductor layer;
• an elongated conductive member continuously formed above said semiconductor layer and said first insulating film, said conductive member having a bottom side that is oriented toward said semiconductor layer, a top side that is oriented away from said semiconductor layer, and first and second sidewalls that extend between said top and bottom sides;
• a second insulating film formed between said conductive member and said semiconductor layer along said conductive member;
• a first sidewall portion formed on said first sidewall of said conductive member and along said conductive member, said first sidewall portion including an oxide film and a first nitride film that is formed above said semiconductor layer and being separated from a region above said first insulating film;
• and
• impurity diffusion regions formed in said semiconductor layer adjacent said first and second sidewall portions,
• wherein said oxide film is a first oxide film that is disposed under said first nitride film,
• wherein said first sidewall portion further comprises a second oxide film formed on said first nitride film,
• wherein said first oxide film and said second oxide film come in contact with each other at a boundary between said semiconductor layer and said first insulating layer,
• wherein said first insulating film is thicker than said semiconductor layer, and
• wherein said conductive member and said first and second oxide films are formed along a step portion at an edge of said first insulating film.