Patent ID: 8088677

Claim:
A method of manufacturing a semiconductor device, comprising: simultaneously implanting an equal amount of an element selected from the group consisting of fluorine and nitrogen into a first transistor-forming region and a second transistor-forming region of a semiconductor substrate; oxidizing said semiconductor substrate to thereby form a first oxide film over said first transistor-forming region and said second transistor-forming region; selectively removing said first oxide film formed over said second transistor-forming region; oxidizing said semiconductor substrate to thereby form a second oxide film at least over said second transistor-forming region, a thickness of said second oxide film being less than a thickness of said first oxide film; forming a first transistor including said first oxide film as a gate insulating film in said first transistor-forming region, and forming a second transistor including said second oxide film as a gate insulating film in said second transistor-forming region; acquiring relations between a dose of said element and threshold voltage values of said first transistor and said second transistor said semiconductor device comprising a plurality of semiconductor devices said plurality of semiconductor devices being manufactured while varying said dose of said element in said implanting said element; and determining said dose of said element based on said relations and depending on target threshold voltage values expected for said semiconductor device to be manufactured.