| 摘要 |
The gate electrode of a high-voltage transistor having a high breakdown voltage is formed from a polysilicon layer having a larger average grain size, so that depletion of the gate electrode easily occurs. By utilizing this depletion, the electrical effective film thickness required by the gate dielectric film of the transistor can be increased. In contrast, the gate electrode of a high-performance transistor needs to have a high speed and a large drive current is formed from a polysilicon layer having a smaller average grain size, so that depletion of the gate electrode hardly occurs. Accordingly, the electrical effective film thickness of the gate dielectric film of the transistor can be maintained at a small value.
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