Abstract
A nitride-based semiconductor device includes a buffer, a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a gate electrode, a first S/D electrode, and a second S/D electrode. The buffer includes at least one layer of a nitride-based semiconductor compound doped with an acceptor at a top-most portion of the buffer. The first nitride-based semiconductor layer is disposed over the buffer. The second nitride-based semiconductor layer is disposed on the first nitride-based semiconductor layer and has a bandgap greater than a bandgap of the first nitride-based semiconductor layer. The gate electrode and the first and second S/D electrodes are disposed over the second nitride-based semiconductor layer. Profiles of the first and second S/D electrodes are asymmetric with respect to the gate electrode, such that a bottom surface of the first S/D electrode is deeper than that of the second S/D electrode with respect to the gate electrode.