A disclosed semiconductor device includes an electron transit layer; an electron supply layer disposed above the electron transit layer; a source electrode, a drain electrode, and a gate electrode, the source electrode, the drain electrode, and the gate electrode being disposed on the electron supply layer; a first capping layer disposed on the electron supply layer between the gate electrode and the drain electrode; and a negative charge generation layer disposed on the first capping layer, the negative charge generation layer being configured to generate a negative charge.