Patent ID: 8125025

Claim:
A semiconductor device comprising: a semiconductor layer including a semiconductor region of one conductivity type; a trench formed in the semiconductor layer so as to penetrate through the semiconductor region, the trench having an open end thereof located at a top surface side of the semiconductor layer; a channel region formed in the semiconductor region so as to lie along a side wall of the trench; and a gate electrode inside the trench with a gate insulating layer interposed between an interior surface of the trench and the gate electrode, wherein the gate electrode is embedded inside the trench such that an upper surface of the gate electrode is located above the semiconductor region, the gate electrode including: a polysilicon layer disposed so that at least part of the polysilicon layer is at a same depth in the semiconductor layer as the channel region with the gate insulating layer interposed between the gate electrode and the channel region, and a low-resistance layer formed on an upper surface of the polysilicon layer and having an electric resistivity lower than an electric resistivity of the polysilicon layer, and wherein a protecting film is formed between the gate insulating layer and the gate electrode above the semiconductor region of one conductivity type such that the protecting film does not face the semiconductor region.