A semiconductor device includes: a first semiconductor layer stacked body including a compound semiconductor; a first field-effect transistor element including a first drain electrode, a first source electrode, and a first gate electrode that are provided on the first semiconductor layer stacked body; a second semiconductor layer stacked body including a compound semiconductor; and a second field-effect transistor element including a second drain electrode, a second source electrode, and a second gate electrode that are provided on the second semiconductor layer stacked body. The second gate electrode forms a Schottky junction or a p-n junction with the second semiconductor layer stacked body, the second drain electrode is connected to the first drain electrode, the second source electrode is connected to the first gate electrode, and the second gate electrode is connected to the first source electrode.