A semiconductor device according to the present invention includes: a semiconductor substrate; a channel layer formed on the semiconductor substrate; a donor layer formed on the channel layer; a first Schottky layer formed on the donor layer; a second Schottky layer formed on the first Schottky layer; a first gate electrode formed on the first Schottky layer to form a Schottky barrier junction with the first Schottky layer; a first source electrode and a first drain electrode formed so as to sandwich the first gate electrode and electrically connected to the channel layer; a second gate electrode formed on the second Schottky layer and made of a material different from the first gate electrode to form a Schottky barrier junction with the second Schottky layer; and a second source electrode and a second drain electrode formed so as to sandwich the second gate electrode and electrically connected to the channel layer.