| 摘要 |
A first polysilicon film, an ONO film, and a second polysilicon film are deposited on a substrate. After ions of an impurity have been implanted in the second polysilicon film, a silicon oxide is deposited on the substrate, followed by a heat treatment for activating the impurity. Patterning is thereafter performed on the silicon oxide film, the second polysilicon film, the ONO film and the first polysilicon film to from stack cell electrodes and an on-gate protective film. The on-gate protective film formed of a silicon oxide film is densified to have improved resistance to etching. Therefore the desired shape of the on-gate protective film is maintained. The film thickness of sidewalls on side surfaces of the stack cell electrodes is set with stability, so that the reduction in insulation withstand voltage between a contact and a control gate electrode is limited.
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