A semiconductor apparatus includes a substrate; a nitride semiconductor layer formed on the substrate; a transistor formed on the nitride semiconductor layer, and including a source electrode, a gate electrode, and a drain electrode disposed in this order; and a diode formed on the nitride semiconductor layer, and including an anode electrode and a cathode electrode disposed in this order. The semiconductor apparatus has a transistor/diode pair in which the source electrode, the gate electrode, the drain electrode, the anode electrode, and the cathode electrode are sequentially disposed in this order, and the drain electrode of the transistor and the anode electrode of the diode are connected by a drain/anode common electrode wiring and serve as a common electrode.