Abstract
A nitride-based semiconductor device includes first and second nitride-based semiconductor layers, a doped III-V semiconductor layer, a gate, a source electrode, and a drain electrode. The doped III-V semiconductor layer is disposed over the second nitride-based semiconductor layer and has opposing first sidewalls that are recessed inward toward a body of the doped III-V semiconductor layer between the sidewalls to form a curved profile at a bottom of the doped III-V semiconductor layer. The gate electrode is disposed over the doped III-V semiconductor layer. The source electrode and the drain electrode are disposed over the second nitride-based semiconductor layer. The gate electrode is located between the source electrode and the drain electrode.