A semiconductor device includes a nitride semiconductor layer, an insulating layer provided on a surface of the nitride semiconductor layer, and a metal electrode in contact with the surface through an opening penetrating the insulating layer. The insulating layer includes a first SiN film having a concentration of chlorine (Cl) of 1×1020 [atoms/cm3] or more and a thickness of 30 nm or less, and a second SiN film having a concentration of chlorine (Cl) of 1×1019 [atoms/cm3] or less.