According to one embodiment, a field-effect transistor includes a source region of a first conductivity type, a drain region of the first conductivity type and a channel region of the first conductivity type between the source region and the drain region, the source region, the drain region and the channel region being disposed in a polycrystalline semiconductor layer; a first layer including an amorphous semiconductor layer disposed on the channel region; a gate insulating layer disposed on the first layer; and a gate electrode disposed on the gate insulating layer.