| 摘要 |
A Trench MOSFET of an embodiment of the present invention includes: a semiconductor substrate including a substrate, an epitaxial layer, a body region, and a highly doped source region. The substrate, the epitaxial layer, the body region, and the highly doped source region are adjacently formed in this order. A trench region is formed in the semiconductor substrate in such a manner that the bottom of the trench region reaches the epitaxial layer. A gate insulator is formed on a bottom surface and a sidewall of the trench region. A gate electrode is provided within the trench region. The gate insulator includes an electric-field reducer thicker than a thickness of the gate insulator provided between the gate electrode and the body region. Thus, voltage-resistance improves in the vicinity of the bottom of the trench. This allows increase of breakdown voltage. Therefore, a Trench MOSFET with higher breakdown voltage is realized.
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