Patent ID: 8664716

Claim:
A semiconductor device including a power MOSFET, comprising: a semiconductor substrate of a first conductive type having a main surface and a rear surface; a first semiconductor region of the first conductive type formed above the main surface of the semiconductor substrate; a second semiconductor region of a second conductive type being opposite to the first conductive type formed in the first semiconductor region; a third semiconductor of the first conductive type formed in the first semiconductor region; a fourth semiconductor of the first conductive type formed in the second semiconductor region; a gate electrode of the power MOSFET formed over the second, third and fourth semiconductor regions; a source electrode of the power MOSFET electrically connected to the fourth semiconductor region; a drain electrode of the power MOSFET formed on the rear surface of the semiconductor substrate and electrically connected to the third semiconductor region; a first trench formed to reach the semiconductor substrate from a surface of the third semiconductor region; and a first conductive film embedded in the first trench via a first insulating film, wherein an impurity concentration of the semiconductor substrate is higher than impurity concentrations of the first and third semiconductor regions, respectively, wherein the impurity concentration of the third semiconductor region is higher than the impurity concentration of the first semiconductor region, and wherein the third semiconductor region is formed along the first trench so as to contact with the semiconductor substrate.