Patent ID: 8421182

Claim:
A field effect transistor having a metal-oxide-semiconductor structure made of nitride compound semiconductor, the field effect transistor comprising: a substrate; a buffer layer formed on the substrate; a reduced surface field layer of a first conductive type formed on the buffer layer; a semiconductor layer of a second conductive type formed on a portion of the reduced surface field layer; a contact layer of the first conductive type formed in or on the semiconductor layer; a source electrode formed on the contact layer; a drain electrode formed on the reduced surface field layer such that the drain electrode does not overlap the semiconductor layer; a gate insulating film formed on the semiconductor layer such that the gate insulating film overlaps with an end portion of the semiconductor layer; and a gate electrode formed on the gate insulating film such that the gate electrode overlaps with the end portion of the semiconductor layer, wherein a channel formed near the end portion of the semiconductor layer is electrically connected to the reduced surface field layer, and wherein the buffer layer, the reduced surface field layer, the semiconductor layer and the contact layer are formed on the substrate in the recited order.