| 摘要 |
The invention provides a trench gate type transistor in which the gate capacitance is reduced, the crystal defect is prevented and the gate breakdown voltage is enhanced. Trenches are formed in an N− type semiconductor layer. A uniformly thick silicon oxide film is formed on the bottom of each of the trenches and near the bottom, being round at corner portions. A silicon oxide film is formed on the upper portion of the sidewall of each of the trenches, which is thinner than the silicon oxide film and round at corner portions. Gate electrodes are formed from inside the trenches onto the outside thereof. The thick silicon oxide film reduces the gate capacitance, and the thin silicon oxide film on the upper portion provides good transistor characteristics. Furthermore, with the round corner portions, the crystal defect does not easily occur, and the gate electric field is dispersed to enhance the gate breakdown voltage.
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