A semiconductor device according to an embodiment of the present invention comprises a packaging substrate mounted with semiconductor chips; a heat dissipation metal plate having three or more sides and mounted with the packaging substrates; a frame provided along an external periphery of the heat dissipation metal plate and encircling the packaging substrates; an adhesive provided to between the heat dissipation metal plate and the frame to bond the heat dissipation metal plate and the frame together; and a sealing resin sealing the semiconductor chips and the packaging substrates within a box formed by the heat dissipation metal plate and the frame, wherein the volume of the adhesive at corners of the heat dissipation metal plate is smaller than that on the sides thereof.