Patent ID: 7235441

Claim:
A manufacturing method of a nonvolatile semiconductor memory device, comprising the steps of: (a) forming a first insulator over a main surface of a semiconductor substrate, and forming a first gate electrode on said first insulator so that a taper angle of a lowermost portion of a sidewall of said first gate electrode with respect to the main surface of said semiconductor substrate can be within a range of 95 to 180 degrees except for 180 degrees; (b) forming a second insulator over the sidewall of said first gate electrode, and forming a third insulator on the surface of said semiconductor substrate on both sides of said first gate electrode; (c) forming a fourth insulator on said second insulator and said third insulator; (d) forming a fifth insulator on said fourth insulator; and (e) forming a second gate electrode made of a conductive material on the sidewall of said first gate electrode and at a position opposite to said semiconductor surface on one or both sides of said first gate electrode via said second to fifth insulators.