The semiconductor device includes: an AlGaN layer; a contact electrode; an insulating film; and a passivation film. The semiconductor device further includes: an extended wire extending over the contact electrode and the insulating film; and a pad electrode electrically connected to the extended wire. The passivation film covers the insulating film and the extended wire and including an opening for exposing the pad electrode. The insulating film accommodates the opening in a plan view. The passivation film accommodates the contact electrode in a plan view. The semiconductor device further includes a heat dissipation layer on a surface of the passivation film.