| 摘要 |
A DMOS transistor in which a main current flows between first and second main surfaces of a silicon substrate is formed. DMOS transistor has a p-type diffusion region formed in the first main surface, an n+ diffusion region formed in the first main surface in p-type diffusion region, and a gate electrode facing p-type diffusion region sandwiched between n+ diffusion region and n- layer via a gate insulating layer. A dielectric layer is formed in the silicon substrate so as to be adjacent to n- layer, and made of a material having a dielectric constant higher than that of silicon. Therefore, the semiconductor device which can be easily formed while suppressing increase in process cost and has an improved trade-off (effective on-state resistance) between a withstand voltage and on-state resistance by generating an electric field almost uniform in the direction of the thickness of a semiconductor substrate can be attained.
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