To provide a semiconductor device capable of more efficiently dissipating heat from a semiconductor chip. The present invention is provided with a die pad (11) having a die-pad primary surface (111) and a die-pad back surface (112), a semiconductor chip (41) mounted on the die-pad primary surface (111), an encapsulating resin part (7) provided with a concave part (75) for exposing the die-pad backsurface (112), the encapsulating resin part covering the die pad (11) and the semiconductor chip (41), and a heat-dissipating layer (6) disposed on the concave part (75). The concave part (75) is positioned in the widening direction of the die-pad back surface (112) and farther outward than the die pad (11), and has a concave groove (753) having a portion positioned farther toward the die-pad primary surface (111) than the die-pad back surface (112). Part of the heat-dissipating layer (6) fills the concave groove (753), and the heat-dissipating layer has a joining layer (66) contacting the die-pad back surface (112).