PURPOSE: To prevent a current drift form being caused by a method wherein an insulating-film laminate composed of the following is used for a gate insulating film: a first insulating film whose main components are nitrogen and phosphorus; a second silicon nitride film laminated on it; and a third silicon dioxide film laminate on them.
CONSTITUTION: The following are laminated on a semi-insulating InP substrate 1: an n-type action layer 2; a source electrode 3s formed on said n-type action layer 2; a drain electrode 3d formed on said n-type action layer 2 so as to be faced with the source electrode 3s; a PN film 4; an SiN film 5; and an SiO 2 film 6. An insulating film 7 is applied to regions excluding parts where the source electrode and the drain electrode are formed on the n-type action layer 2; in addition, it is formed so as to be extended to end parts on the surface of both the source electrode and the drain electrode. A source pad electrode 8S is formed on the source electrode 3s and a drain pad electrode 8D is formed on the drain electrode 3d. In addition, a gate electrode 3g is formed on the insulating film 7 between the source electrode 3s and the drain electrode 3d which are faced with each other. Thereby, an InP MISFET is constituted.