Abstract: A semiconductor device includes a first semiconductor layer provided over a substrate; an electron transit layer contacting a top of the first semiconductor layer; and a second semiconductor layer contacting a top of the electron transit layer, wherein the electron transit layer has a dual quantum well layer having a structure where a first well layer, an intermediate barrier layer, and a second well layer are sequentially stacked, an energy of a conduction band of the intermediate barrier layer is lower than an energy of conduction band of the first semiconductor layer and the second semiconductor layer, and a ground level is generated in the first and second well layers, and a first excitation level is generated in the dual quantum well layer.