Abstract
A semiconductor device includes a first and a second nitride-based semiconductor layers, a source electrode, a drain electrode, a gate electrode, and a first and a second stress modulation layers. The first nitride-based semiconductor layer has a first thickness. The second nitride-based semiconductor layer has a bandgap less than a bandgap of the first nitride-based semiconductor layer to form a heterojunction therebetween. The second nitride-based semiconductor layer has a second thickness, and a ratio of the first thickness to the second thickness is in a range from 0.5 to 5. The first and the second stress modulation layers provide a first and a second drift regions of the second nitride-based semiconductor layer with stress, respectively, resulting in induction of a first and a second 2DHG regions within the first and the second drift regions, respectively.