Patent ID: 7605426

Claim:
A power semiconductor device comprising: a semiconductor substrate; a gate insulating film; a control electrode insulated from the semiconductor substrate by the gate insulating film; a first main electrode provided on a lower surface side of the semiconductor substrate; and a second main electrode provided on an upper surface side of the semiconductor substrate, the semiconductor substrate including: a first first-conductivity-type semiconductor layer with its lower surface connected to the first main electrode; a second first-conductivity-type semiconductor layer and a third second-conductivity-type semiconductor layer formed on the first first-conductivity-type semiconductor layer and alternately arranged parallel to the upper surface of the semiconductor substrate; a trench formed in a directly overlying region of the third second-conductivity-type semiconductor layer, with part of the second main electrode buried in the trench; a fourth second-conductivity-type semiconductor layer selectively formed in a surface of the second first-conductivity-type semiconductor layer and connected to the second main electrode; a fifth first-conductivity-type semiconductor layer selectively formed in a surface of the fourth second-conductivity-type semiconductor layer and connected to the second main electrode; and a sixth second-conductivity-type semiconductor layer formed at a bottom of the trench and connected to the second main electrode, impurity concentration in the sixth second-conductivity-type semiconductor layer being higher than impurity concentration in the fourth second-conductivity-type semiconductor layer, and lower surface of the sixth second-conductivity-type semiconductor layer being located below lower surface of the fourth second-conductivity-type semiconductor layer.