The present disclosure, in some embodiments, relates to a semiconductor device. The semiconductor device includes an electron supply layer that is disposed over an upper surface of a semiconductor material and that is laterally arranged between a first conductive terminal and a second conductive terminal. A III-N (III-nitride) semiconductor material is disposed over the electron supply layer. A passivation layer is disposed over the III-N semiconductor material, along a side of the III-N semiconductor material, and over the electron supply layer. An insulating material is arranged over the passivation layer and along opposing sidewalls of the second conductive terminal, and a gate structure is disposed over the passivation layer. The passivation layer has an uppermost surface that is directly coupled to a sidewall of the passivation layer. The insulating material extends along the sidewall of the passivation layer.