A semiconductor device includes a switching device having: a substrate configured by a semi-insulating material or a semiconductor; a channel forming layer on the substrate that is configured by a compound semiconductor mainly having a group III nitride; a gate structure configured by a gate electrode on the channel forming layer with a gate insulating film interposed therebetween; and a source electrode and a drain electrode on the channel forming layer at both sides of the gate structure respectively, a collapse inhibiting layer on the channel forming layer in an element region of the channel forming layer where the switching device is arranged that is configured by an insulating material; and a leakage inhibiting layer on the channel forming layer in an element isolation region of the channel forming layer surrounding the element region that is configured by an insulating material different from that of the collapse inhibiting layer.