A semiconductor device has a first semiconductor layer, a second semiconductor layer, and an active layer sandwiched between the first and the second semiconductor layer and emits light from the active layer when a voltage is applied across the first and the second semiconductor layer. The semiconductor device includes an anode on the first semiconductor layer, an insulating film on the anode, and a screen electrode on the insulating film covering at least part of the anode. The second semiconductor layer is grounded and the screen electrode is electrically connected to the grounded second semiconductor layer. The screen electrode screens the anode to prevent flow of a leakage current between the first and second semiconductor layers due to electromagnetic waves.