Semiconductor device

A semiconductor device as a transistor, having a semiconductor layer comprising Group III nitride semiconductor or gallium oxide-based semiconductor, the semiconductor device comprising:

• a trench with an inner surface which is covered with a gate insulating film, the trench having a gate electrode therein;
• a first n-type layer, a p-type layer, and a second n-type layer which are sequentially deposited;
• a recess reaching the p-type layer from the surface of the second n-type layer;
• and
• a body electrode in contact with the p-type layer exposed on a bottom surface of the recess,
• wherein
• the p-type layer comprises:
• a third p-type layer disposed in contact with the first n-type layer;
• a first p-type layer disposed in contact with the third p-type layer, the first p-type layer having an acceptor concentration lower than an acceptor concentration of the third p-type layer;
• and
• a second p-type layer deposited on the first p-type layer, the second p-type layer having an acceptor concentration higher than the acceptor concentration of the first p-type layer and not lower than the acceptor concentration of the third p-type layer, and
• the recess has a depth reaching the second p-type layer,
• side surfaces of the third p-type layer, the first p-type layer, and the second p-type layer are in contact with a side surface of the gate insulating film, respectively, all of the side surfaces being a region serving as a channel of the transistor, and
• a bottom surface of the body electrode is in contact with the second p-type layer exposed on the bottom surface of the recess.