A semiconductor device includes a semiconductor element, a mounting pad on which the semiconductor element is mounted; first internal leads electrically connected to the semiconductor element; a heat radiation plate spaced from and opposite the semiconductor element with the mounting pad and located between the heat radiation plate and the semiconductor element, the heat radiation plate having a second internal lead; a sealing material encapsulating the semiconductor element, the mounting pad, the first and second internal leads, and part of the heat radiation plate; external leads continuing from the first internal leads and extending outside of the sealing material; and a grounding lead continuous with and extending from the second internal lead of the heat radiation plate, outside of the sealing material, for mechanically mounting and electrically grounding the heat radiation plate.