The semiconductor unit includes a wiring board, a conductor layer and a fin. The wiring board has across a thickness thereof a first surface and a second surface. The conductor layer is formed on the first surface of the wiring board. The conductor layer has a length and a width as viewed in the direction of the thickness of the wiring board. The fin is joined to the second surface of the wiring board. The fin has a bent edge that extends in the direction of the length of the conductor layer.