A semiconductor device includes at least first and second electrodes, and a layer including a transition metal oxide layer sandwiched between the first and second electrodes. The transition metal oxide layer includes first and second transition metal oxide layers formed of different first and second transition metals, respectively. The first transition metal oxide layer is provided on the first electrode side, the second transition metal oxide layer is provided on the second electrode side, the first transition metal oxide layer and the second transition metal oxide layer are in contact with each other, the first transition metal oxide layer has an oxygen concentration gradient from the interface between the first transition metal oxide layer and the second transition metal oxide layer toward the first electrode side, and the oxygen concentration at the interface is greater than the oxygen concentration on the first electrode side.