US Patent 7919811 Semiconductor device and method for manufacturing same

A semiconductor device includes a second-conductivity-type base region provided on a first-conductivity-type semiconductor layer, a first-conductivity-type source region provided on the second-conductivity-type base region, a gate insulating film covering an inner wall of a trench which passes through the second-conductivity-type base region and reaching the first-conductivity-type semiconductor layer, a gate electrode buried in the trench via the gate insulating film, and a second-conductivity-type region being adjacent to the second-conductivity-type base region below the first-conductivity-type source region, spaced from the gate insulating film, and having a higher impurity concentration than the second-conductivity-type base region. c≧d is satisfied, where d is a depth from an upper surface of the first-conductivity-type source region to a lower end of the gate electrode, and c is a depth from an upper surface of the first-conductivity-type source region to a lower surface of the second-conductivity-type base region.