A semiconductor device which includes a radiating plate, a wiring patterned layer on the radiating plate via an insulating layer, at least one semiconductor chip mounted on the wiring patterned layer. The semiconductor chip has a surface electrode. The semiconductor device further includes a conductive lead plate electrically connected with the surface electrode of the semiconductor chip, and a resin package of thermoplastic resin having anisotropic linear expansion coefficient varying based upon directions. The resin package covers the wiring patterned layer, the semiconductor chip, the conductive lead plate, and at least a portion of the radiating plate. The conductive lead plate extends in a direction which provides the resin package with the maximum linear expansion coefficient. In the semiconductor device so structured, the warpage of the resin package is reduced both in longitudinal and transverse directions.