Some embodiments of the disclosure provide a semiconductor device. The semiconductor device comprises: a substrate; a first nitride semiconductor layer on the substrate; a second nitride semiconductor layer on the first nitride semiconductor layer and having a band gap greater than a band gap of the first nitride semiconductor layer; a group III-V dielectric layer disposed on the second nitride semiconductor layer; a gate electrode disposed on the second nitride semiconductor layer; and a first passivation layer disposed on the group III-V dielectric layer, wherein the group III-V dielectric layer is separated from the gate electrode by the first passivation layer.