Semiconductor device and method for manufacturing the same
A semiconductor device includes a first and a second nitride-based semiconductor layers, a gate electrode, and a doped nitride-based semiconductor layer. The doped nitride-based semiconductor layer is disposed between the second nitride-based semiconductor layer and the gate electrode. The doped nitride-based semiconductor layer has a pair of opposite ledge portions free from coverage of the gate electrode and a central portion therebetween. The second nitride-based semiconductor layer has a first portion beneath the central portion and a second portion beneath the ledge portion, and the second nitride-based semiconductor layer has a doping concentration of a dopant that selected from a highly electronegative group, in which the doping concentration from the first portion to the second portion increases.
1 . A semiconductor device, comprising:
a first nitride-based semiconductor layer;
a second nitride-based semiconductor layer disposed on the first nitride-based semiconductor layer and having a bandgap greater than a bandgap of the first nitride-based semiconductor layer;
a gate electrode disposed above the second nitride-based semiconductor layer; and
a doped nitride-based semiconductor layer disposed between the second nitride-based semiconductor layer and the gate electrode, the doped nitride-based semiconductor layer having a pair of opposite ledge portions free from coverage of the gate electrode and a central portion therebetween, wherein the second nitride-based semiconductor layer has a first portion beneath the central portion and a pair of opposite second portions beneath the corresponding ledge portion of the pair of ledge portions, and the second nitride-based semiconductor layer has a doping concentration of a dopant that selected from a highly electronegative group, wherein the doping concentration from the first portion to the pair of opposite second portions increases;
wherein a first dielectric layer disposed on the gate electrode; and
a second dielectric layer covers the first dielectric layer and the pair of opposite ledge portions of the doped nitride-based semiconductor layer, and two opposite side surfaces of the doped nitride-based semiconductor layer are free from coverage by the second dielectric layer.
2 . The semiconductor device of claim 1 , wherein the increase of the doping concentration of the second nitride-based semiconductor layer is continuous.
3 . The semiconductor device of claim 1 , wherein the doping concentration of the first portion of the second nitride-based semiconductor layer is zero.
4 . The semiconductor device of claim 1 , wherein the second nitride-based semiconductor layer has a third portion abutting against the second portion, and the doping concentration of the third portion is less than that of the second portion of the second nitride-based semiconductor layer.
5 . The semiconductor device of claim 4 , wherein the doping concentration of the third portion of the second nitride-based semiconductor layer is zero at a top surface thereof.
6 . The semiconductor device of claim 4 , wherein the doped nitride-based semiconductor layer has a side surface extending upward from an interface between the second and third portions of the second nitride-based semiconductor layer.
7 . The semiconductor device of claim 1 , wherein each of the ledge portions of the doped nitride-based semiconductor layer is doped to have a doping concentration of the dopant less than that of the second portion of the second nitride-based semiconductor layer.
8 . The semiconductor device of claim 1 , wherein the doping concentration of the second portion of the second nitride-based semiconductor layer remains constant along a thickness direction thereof.
9 . The semiconductor device of claim 1 , further comprising:
the first dielectric layer having a pair of opposite side surfaces which connect two opposite side surfaces of the gate electrode, respectively.
10 . The semiconductor device of claim 9 , further comprising:
the second dielectric layer disposed on the doped nitride-based semiconductor layer and covering the side surfaces of the gate electrode.