Importance

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Abstract

A vertical trench MISFET is provided that includes a semiconductor substrate having a first conductivity type semiconductor, and a second conductivity type impurity layer provided on the first conductivity type semiconductor. A trench extends from a surface of the semiconductor substrate to reach said first conductivity type semiconductor. A second conductivity type base region is formed in a top portion of the semiconductor substrate, and a first conductivity type source region is formed in a part of a surface layer of the second conductivity type base region. A first conductivity type drain drift region having a small thickness is formed in a surface layer of a side wall of the trench. The drain drift region has a higher impurity concentration than a level at which a breakdown voltage measured in a hypothetical diffusion type junction is substantially equal to an element withstand voltage. A gate electrode is formed on an exposed surface of the second conductivity type base region, through a gate insulating film. A source electrode is disposed in contact with surfaces of both of the first conductivity type source region and the second conductivity type base region, while a drain electrode is disposed in contact with a rear surface of the first conductivity type semiconductor.

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First Claim