Patent ID: 6927132

Claim:
A method for producing a nonvolatile semiconductor memory device, comprising: forming a first insulating film on a semiconductor substrate; forming a floating gate electrode material film on the first insulating film; forming a second insulating film on the floating gate electrode material film; forming a control gate electrode material film on the second insulating film; forming a first mask film on the control gate electrode material film, the first mask film having slits extending along a first direction; forming sidewalls on the sides of the first mask film in the slits so that the sidewalls cover a whole side of the first mask film and have a sloped surface; and etching the control gate electrode material film, the second insulating film and the floating gate electrode material film using the first mask film and the sidewalls as a mask so as to align and flatten etched side surfaces of the control gate electrode material film, etched side surfaces of the second insulating film and etched side surfaces of the floating gate electrode material film and so as to form memory cells each of which includes a floating gate electrode and a control gate electrode.