A method for manufacturing a semiconductor device comprises preparing a base; forming a silicon oxide film including hydrogen or deuterium on the base; diffusing nitrogen into the silicon oxide film to form a gate insulating film; forming a gate electrode on the gate insulating film; ion doping the base to form source and drain regions along side a channel region; and forming a source electrode connected to the source region and a drain electrode connected to the drain region, the gate insulating film having a region where B/A is in the range of 1.6 to 10, where A is a concentration of nitrogen, and B is a concentration of hydrogen or deuterium, and the region is Y/10 of the thickness of the gate insulating film from the interface between the gate insulating film and the base, where Y is an average thickness of the gate insulating film.