Patent ID: 7601576

Claim:
A method for fabricating a semiconductor device comprising the steps of: forming on a semiconductor substrate a mask film including a first insulation film whose etching characteristics are different from etching characteristics of the semiconductor substrate, and a second insulation film having a width smaller than a width of the first insulation film and having etching characteristics different from the etching characteristics of the first insulation film, the second insulation film being formed over the first insulation film; etching the semiconductor substrate with the mask film as a mask to form a device isolation trench defining an active region; forming a third insulation film on the semiconductor substrate with the device isolation trench formed in; and removing the third insulation film on the second insulation film to form a device isolation film buried in the device isolation trench and having a projected part composed of the third insulation film projected over a peripheral edge of the active region, the projected part covering the peripheral edge.