Semiconductor device and methods for their preparation

A semiconductor device comprising a first III-V compound layer on a substrate, a second III-V compound layer on the first III-V compound layer, wherein a material of the first III-V compound layer of the second III-V compound layer differs, a gate metal stack, which is disposed on the second III-V compound layer, a source contact and a drain contact which are arranged on opposite sides of the gate metal stack, a gate field plate, which is arranged between the gate metal stack and the drain contact, a Antireflexionsbeschichtungs- (ARC ) layer that is formed on the source contact and the drain contact, and an etch stop layer that is formed on the ARC layer.