COMPOUND SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a compound semiconductor device which has a high threshold voltage and superior normally-off characteristics.SOLUTION: The compound semiconductor device includes a compound semiconductor layer 2, in which a two-dimensional carrier gas layer 211 is formed, the compound semiconductor layer, including a carrier travel layer 21 and a carrier supply layer 22; first and second main electrodes 3 and 4, which are arranged separated from each other on the compound semiconductor layer 2 and are ohmically connected to the two-dimensional carrier gas layer 211; a metal oxide semiconductor film 8, arranged on the compound semiconductor layer 2 between the first main electrode 3 and the second main electrode 4; and a control electrode 5 arranged on the metal oxide semiconductor film 8, the control electrode, including a titanium film that contacts the metal oxide semiconductor film or a titanium-containing compound film that contacts the metal oxide semiconductor film 8.