Patent ID: 8193056

Claim:
A method of manufacturing a semiconductor device, comprising the steps of: forming a tunnel insulating film on a semiconductor substrate; forming a floating gate electrode on the tunnel insulating film; forming a silicon nitride film including a low-density silicon nitride film and a high-density silicon nitride film on the floating gate electrode; forming an isolation trench by processing the silicon nitride film, the floating gate electrode, the tunnel insulating film, and the semiconductor substrate, and thereby exposing the low-density silicon nitride film at least in a portion of a side surface of the isolation trench; forming an isolating insulating film which covers an internal surface of the isolation trench; flattening the isolating insulating film; etching the isolating insulating film and thereby lowering a top surface of the isolating insulating film; removing the silicon nitride film; and forming an interelectrode insulating film and a control gate electrode which cover the floating gate electrode and the isolating insulating film.