Abstract
A semiconductor device includes a first nitride-based semiconductor layer, a second nitride-based semiconductor layer, a pair of first electrodes, a second electrode, a doped nitride-based semiconductor layer, and a pair of gate electrodes. The second nitride-based semiconductor layer is disposed on the first nitride-based semiconductor layer. The first and second nitride-based semiconductor layers collectively have an active portion and an electrically isolating portion that is non-semi-conducting and surrounds the active portion to form an interface therebetween. The first electrodes are disposed over the second nitride-based semiconductor layer. The second electrode are disposed over the second nitride-based semiconductor layer and between the first electrodes. The doped nitride-based semiconductor layer is disposed over the second nitride-based semiconductor layer and between the first electrodes and surrounding the second electrode. The gate electrodes are disposed over the doped nitride-based semiconductor layer and located at opposite sides of the second electrode.