The semiconductor device comprises a support plate; a semiconductor element; and conductor posts consisting of a conductor having a first end at one end and a second end at the other end, the second end being connected to the semiconductor element and the conductor posts being connected to the support plate at a position on the side of the second end that is closer to the first end, wherein the conductor posts have a heat conductivity of approximately 200 W/m·K or higher and a Vickers hardness of approximately 70 or lower.