A semiconductor device has a semiconductor substrate including a body region, a drift region, a trench that extends from a surface of the semiconductor substrate into the drift region through the body region, and a source region located adjacent to the trench in a range exposed to the surface of the semiconductor substrate, the source region being isolated from the drift region by the body region. A specific layer is disposed on a bottom of the trench, and it has a characteristic of forming a depletion layer at a junction between the specific layer and the drift region. An insulating layer covers an upper surface of the specific layer and a sidewall of the trench. A conductive portion is formed on a part of the side wall of the trench. The conductive portion is joined to the specific layer, and reaches the surface of the semiconductor substrate.