Semiconductor device and method of fabricating the same

A method of fabricating a semiconductor device comprising:

• forming a recess in a semiconductor substrate, the recess having a bottom and opposite sidewalls substantially at a right angle to the bottom;
• and
• forming a first gate insulating film in the recess and a second gate insulating film on a part of the substrate other than the recess, the first gate insulating film having a first film thickness larger than a second film thickness of the second gate insulating film, wherein the first and second gate insulating films have respective upper surfaces which are substantially on a level with each other.

A method of fabricating a semiconductor device comprising:

• forming two gate insulating films with first and second film thicknesses on a semiconductor substrate respectively, the second film thickness being smaller than the first film thickness;
• and
• forming on the gate insulating films two polycrystalline silicon films with third and fourth film thicknesses so that upper surfaces of the polycrystalline silicon films are substantially on a level with each other, the polycrystalline silicon films serving as gate electrodes.