Nonvolatile semiconductor memory device and method for manufacturing the same

Abstract

A nonvolatile semiconductor memory device includes erasable and programmable memory cell transistors, a selection transistor, a peripheral transistor, first post-oxidation films each provided on a gate electrode of all of the plurality of erasable and programmable memory cell transistors, a second post-oxidation film provided on a gate electrode of the selection transistor, a third post-oxidation film provided on a gate electrode of the peripheral transistor, and an insulating film covering the memory cell transistors, the selection transistor, and the peripheral transistor. The insulating film is harder for an oxidizing agent to pass through than a silicon oxide film. The insulating film has an oxidized region. The insulating film includes a silicon nitride film. The oxidized region is provided in a surface of the silicon nitride film.