The disclosure relates to a semiconductor device. In an embodiment, a semiconductor device includes an enhancement mode Group III-nitride-based High Electron Mobility Transistor (HEMT) including a drain, a gate, a barrier layer, a channel layer, a barrier layer arranged on the channel layer, and a heterojunction formed between the barrier layer and the channel layer and capable of supporting a two-dimensional electron gas (2DEG). At least one of a thickness and a composition of the barrier layer is configured to decrease a 2DEG density in a channel region compared with a 2DEG density outside of the channel region, wherein the channel region is arranged under the gate and extends a distance d beyond a drain-sided gate edge.