In a semiconductor device including a crystalline nitride layer, in which diamond is used for heat dissipation thereof, it is an object of the present invention to suppress cracking of the crystalline nitride layer. The semiconductor device includes a layered body and a heat dissipation layer. The layered body includes a crystalline nitride layer and a composite layer. The composite layer includes a non-inhibiting portion which does not inhibit diamond growth on a surface thereof and an inhibiting portion which inhibits the diamond growth on the surface. A layered body main surface of the layered body has a first region in which the non-inhibiting portion is exposed and a second region in which the inhibiting portion is exposed. The heat dissipation layer is made of diamond, opposed to the main surface, adhered to the first region, and separated from the second region with a void interposed therebetween.