A semiconductor device comprises a substrate; a primary semiconductor die attached onto the substrate comprising a front surface and a back surface, wherein the primary semiconductor die has a first region and a second region besides the first region; an auxiliary semiconductor die attached onto the front surface at the first region; a heat transfer block comprising a main body attached onto the front surface at the second region; a metal layer wrapping around the main body; a graphene layer formed outside of the metal layer; a heat spreader attached onto the substrate and defining with the substrate a chamber for accommodating the primary semiconductor die, the auxiliary semiconductor die and the heat transfer block, wherein the graphene layer extends between the heat spreader and the front surface such that heat generated by the first region can be transferred to the heat spreader through the graphene layer.