A high-electron-mobility transistor comprises a semiconductor body comprising a barrier region and a channel region that forms a heterojunction with the barrier region such that a two-dimensional charge carrier gas channel is disposed in the channel region, source and drain electrodes disposed on the semiconductor body and laterally spaced apart from one another, a gate structure disposed on the semiconductor body and laterally between the source and drain electrodes, the gate structure being configured to control a conduction state of two-dimensional charge carrier gas, and a first dielectric region that is disposed along the upper surface of the semiconductor body in a lateral region that is between the gate structure and the drain electrode, wherein the first dielectric region comprises aluminum and oxide, and wherein first dielectric region comprises a first end that faces and is laterally spaced apart from the gate structure.