PURPOSE: To prevent Schottky characteristics due to annealing by selectively ion implanting and annealing a high melting point metal gate metal film in the state formed on the overall semiconductor substrate, and then forming a gate electrode.

CONSTITUTION: After Si ions are implanted to a semiinsulating GaAs substrate 6 with a resist film as a mask, the resist film is removed, an SiO2 film is formed on the overall GaAs substrate 6, annealed to form an operation layer 4. Then, the SiO2 film is removed, W is accumulated on the substrate 6, a CVDSiO2 film 7 is formed on the film 1, and the film 7 of the region except the gate electrode film is removed. Then, the regions except the gate, source and drain regions is coated with a resist film 8, Si ions are implanted, and a high density impurity region 5 is formed. Then, the film 8 is removed, annealed, the film 1 is removed, and a gate electrode is formed. Subsequently, the region except the source and drain electrodes is coated with a resist film, AuGe/Ni is deposited, the resist film is then removed to form source, drain electrodes 2, 3.