| 摘要 |
A nonvolatile semiconductor memory device includes an element isolation insulating film buried in first trenches, a floating gate electrode formed on an element forming region with a first gate insulating film being interposed between them, and a second gate insulating film formed on upper portions of the floating gate electrode and an element isolation insulating film. The floating gate electrode is formed so as to have a side that extends from a bottom thereof to its upper portion and is substantially an extension of a sidewall of each first trench. The element isolation insulating film includes a portion located between its sidewall and the sidewall of a second trench, and the portion of the element isolation insulating film having a film thickness in a direction along the upper surface of the semiconductor substrate. The film thickness is equal to a film thickness of the second gate insulating film.
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