In one embodiment, a semiconductor device includes a substrate, and a source region of a first conductivity type disposed on a surface of the substrate. The device further includes a tunnel insulator disposed on the source region, and an impurity semiconductor layer of a second conductivity type disposed on the tunnel insulator, the second conductivity type being different from the first conductivity type. The device further includes a gate insulator disposed on the impurity semiconductor layer, and a gate electrode disposed on the gate insulator. The device further includes a drain region of the second conductivity type disposed on the substrate so as to be separated from the impurity semiconductor layer, or disposed on the substrate as a portion of the impurity semiconductor layer.