According one embodiment, a semiconductor device includes: a first electrode; a second electrode; a first semiconductor layer provided between the first electrode and the second electrode and being in contact with the first electrode; a second semiconductor layer including a first part and a second part, and the second part being contact with the first electrode, and the second semiconductor layer having an effective impurity concentration lower than an effective impurity concentration in the first semiconductor layer; a third semiconductor layer provided between the second semiconductor layer and the second electrode, and having an effective impurity concentration lower than an effective impurity concentration in the second semiconductor layer; and a fourth semiconductor layer provided between the third semiconductor layer and the second electrode, and being in contact with the second electrode.