PURPOSE: To enable the gap between electrodes to be kep to the necessary minimum with good accuracy by a method wherein a semiconductor layer of high resistance which covers the gate electrode and a semiconductor layer continuous to that layer are formed, and a source electrode and a drain electrode with a gap between the gate electrode restricted by the semiconductor layer of high resistance are formed.

CONSTITUTION: The gate electrode 14 is formed on a III-V group semiconductor layer 13 of one conductivity type on a III-V group semi-insulation substrate 11, and a III-V group high-resistant semiconductor layer 15A which covers the gate electrode 14 and a III-V group semiconductor layer 15 of one conductivity type which is continuous to this semiconductor layer and covers said semiconductor layer 13 are provided. Besides, the source electrode 16S and the drain electrode 16D which contact the III-V group high-resistant semiconductor layer 15A whose edge covers the gat eelectrode 14 and which are restricted in the gap between this electrode 14 by said semiconductor layer 15A are provided. This manner can realize the gap between each electrode with accuracy always in the necessary minimum condition because the side wall of the gate electrode is covered with the III-V group high-resistant semiconductor layer and because the gap between each electrode is in self-alignment by the thickness of this high-resistant semiconductor layer.