A channel layer made of undoped InGaAs, a carrier supply layer made of n-type AlGaAs, a Schottky layer made of disordered InGaP without a natural superlattice structure, and a cap layer made of GaAs are successively stacked on a compound semiconductor substrate. A gate electrode is formed on a part of the Schottky layer exposed at the opening of the cap layer. Source and dram electrodes are formed on the cap layer. The thickness of the Schottky layer is set at about 8 nm or less. As a result, the reverse breakdown voltage of the gate electrode becomes larger than that in the case of a Schottky layer made of AlGaAs.