Patent ID: 6849919

Claim:
A method of fabricating a semiconductor device, comprising the steps of: providing a first stopper film on a main surface of a semiconductor substrate; with said first stopper film used as a mask, providing a first recess in a main surface of said semiconductor substrate; filling said first recess with a first insulation film; removing said first insulation film in said first recess to expose at least a portion of a surface of said semiconductor substrate defining a bottom of said first recess, and allowing a remainder of said first insulation film to serve as a second stopper film; with said second stopper film used as a mask, providing a second recess in a surface of said semiconductor substrate defining a bottom of said first recess; with said first recess having said second stopper film remaining therein, providing a second insulation film in said first recess and said second recess; providing a layer of a nitride film to cover a surface of said second insulation film provided in said first recess and said second recess; and providing a third insulation film on said nitride film to fill said first recess and said second recess.