Patent ID: 7968399

Claim:
A method for manufacturing a nonvolatile semiconductor memory device, comprising: forming a first insulating film on a semiconductor substrate; forming a first electrode material film on the first insulating film; forming a stopper film on the first electrode material film; etching the first electrode material film, the first insulating film and the semiconductor substrate so as to form a trench; forming a second insulating film in the trench; flatting the second insulating film used the stopper film as a stopper; etching the second insulating film so that an upper-edge portion of the second insulating film is lower than an upper surface of the first electrode material film and higher than an upper surface of the semiconductor substrate and an upper-middle portion of the second insulating film is lower than the uppert most portion; forming a third insulating film along the upper surface of the first electrode material film and an upper surface of the second insulating film; forming a second electrode material film on the third insulating film, wherein a whole lower side surface, facing to an upper side surface of the second insulating film, of the first electrode material film faces to an inner surface located between the upper-edge portion and the upper-middle portion of the second insulating film.