A compound semiconductor device includes a substrate, a p-type first semiconductor layer over the substrate and contains antimony, a p-type second semiconductor layer over the first semiconductor layer and contains antimony, an n-type third semiconductor layer over the second semiconductor layer, a fourth semiconductor layer between the first semiconductor layer and the second semiconductor layer, the fourth semiconductor layer containing phosphorus and having a thickness in which electrons tunnel between the first semiconductor layer and the second semiconductor layer, a first electrode in ohmic contact with the first semiconductor layer, and a second electrode in ohmic contact with the third semiconductor layer. The first semiconductor layer is made from a material whose contact resistance with the first electrode is lower than contact resistance of the second semiconductor layer.