Patent ID: 7534682

Claim:
A method of fabricating a semiconductor memory device comprising: forming a first insulating film on a semiconductor substrate; patterning the first insulating film to leave the first insulating film on a first and a second element region; etching the semiconductor substrate by use of the first insulating film as a mask to make a plurality of trenches in the semiconductor substrate; etching the side face of the first insulating film on the second element region, while protecting the first insulating film on the first element region; forming a second insulating film on the semiconductor substrate to fill the trenches; etching the second insulating film by use of the first insulating film as a stopper; removing the first insulating film so as to form a first and a second element isolating region with which the trenches are filled and the upper parts of which project from the surface of the semiconductor substrate and enclose the first and second element regions respectively; forming a first gate insulating film on the first and second element regions; removing the first gate insulating film on the second element region, while protecting the first gate insulating film on the first element region and the first element isolating region; forming on the second element region a second gate insulating film thinner than the first gate insulating film, while protecting the first gate insulating film on the first element region; and forming gate electrodes on the first and second gate insulating films.