| 摘要 |
A semiconductor device and its manufacturing method are provided to prevent the phenomenon of polysilicon depletion and to restrain the degradation of refresh characteristics in an NMOS(N channel Metal Oxide Semiconductor) FET(Field Effect Transistor) of a cell. A cell region for NMOSFET and a peripheral region for PMOS FET and NMOSFET are defined on a silicon substrate(21). A first gate oxide layer(25) is formed on NMOSFET forming portions of the cell and peripheral regions. A second gate oxide layer(29) with a nitride layer(30) is formed on a PMOSFET forming portion of the peripheral region. An N+ polysilicon gate is formed on the first gate oxide layer. A P+ polysilicon gate is formed on the second gate oxide layer.
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