Patent ID: 7834393

Claim:
A semiconductor device, comprising: a power MOSFET including a trench formed on a surface of a semiconductor layer forming a drain; a gate electrode formed in the trench via a gate insulation film and made of poly-silicon; a channel diffusion layer formed at a surface side of the semiconductor layer, shallower than the trench and neighboring the trench; and a source diffusion layer formed at a surface side of the channel diffusion layer, and neighboring the trench; wherein a reverse impurity layer is provided on a bottom part side of the trench in the poly-silicon forming the gate electrode, with a gap between the reverse impurity layer and the gate insulation film of an inside side surface of the trench; and an impurity ion that is a conductive type opposite to the conductive type of an impurity ion provided in the poly-silicon forming the gate electrode at a surface side of the trench is provided in the reverse impurity layer.