A semiconductor device, including a circuit pattern, a contact part and an external connection terminal. The contact part has a cylindrical through-hole and first and second opening ends opposite to each other, the second opening end being joined to the circuit pattern. The external connection terminal has a prismatic main body portion and first and second end portions, the second end portion being inserted into the through-hole from the first opening end of the contact part. The main body portion of the external connection terminal has an insertion prevented portion formed thereon. The contact part includes an insertion preventing portion formed on an inner circumferential surface of the through-hole, the insertion preventing portion being so positioned as to be substantially downstream, with respect to an insertion direction of the external connection terminal, from the main body portion of the external connection terminal inserted into the through-hole.