PURPOSE: To obtain excellent high frequency characteristic by providing a recess only on the area of semiconductor substrate with which a schottky barrier type gate electrode is placed in contact.

CONSTITUTION: A transformating layer 8 is formed in the specified depth and width at the contact area of an electrode 7 and epitaxial layer 2 by irradiating the oxygen plasma for the specifed period to a Schottky barrier gate FET forming a source electrode, drain electrode and gate electrode 7. Then, a recess 9 is formed by selectively etching the layer 8 with the electrode 7 used as the electrode in such a way that the contact length lgo between the electrode 7 and layer 2 is in the relation lgo<lg for the gate length lg. Thereby, a sub-micron gate can be formed, improving a high frequency characteristic.