Abstract
A nitride-based semiconductor device includes a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a source electrode, a drain electrode, a gate electrode, and a third nitride-based semiconductor layer. The first nitride-based semiconductor layer has at least one trench. The second nitride-based semiconductor layer is disposed on the first nitride-based semiconductor layer and is spaced apart from the trench. The source electrode and the drain electrode are disposed over the second nitride-based semiconductor layer. The gate electrode is disposed over the second nitride-based semiconductor layer and between the source electrode and the drain electrode so as to define at least a drift region between the gate electrode and the drain electrode and overlapping the trench. The third nitride-based semiconductor layer is disposed at least in the trench and extends upward from the trench to contact the second nitride-based semiconductor layer.