Patent ID: 8710572

Claim:
A nonvolatile semiconductor storage device comprising: a semiconductor substrate; a source region and a drain region that are formed in the semiconductor substrate so as to be separated from each other and so as to define a channel region therebetween; a tunnel insulating film that is formed on the channel region; a charge storage film that is formed on the tunnel insulating film and comprises an insulative charge storage film and floating a conductive charge storage film, the floating conductive charge storage film being shorter than the insulative charge storage film in a channel direction; an interlayer insulating film that is formed on the charge storage film; a gate electrode that is formed on the interlayer insulating film, wherein a source-side end of the floating conductive charge storage film is inwardly positioned as compared with a source-side end of the insulative charge storage film, while a drain-side end of floating the conductive charge storage film is inwardly positioned as compared with a drain-side end of the insulative charge storage film; and side insulating films that are formed on sides of the floating conductive charge storage film.