SEMICONDUCTOR DEVICE
A semiconductor device includes a first hetero-junction body in which a first channel layer and a first barrier layer are bonded together; a second hetero-junction body in which a second channel layer formed on the first hetero-junction body and a second barrier layer are bonded together; a gate electrode in Schottky contact with the second barrier layer; and source and drain electrodes in ohmic contact with the first and second hetero-junction bodies. At least one of the first and second channel layers has such a thickness that an electron concentration in a 2DEG layer formed in the channel layer is not reduced.
1 . A semiconductor device comprising:
a first hetero-junction body in which a first nitride semiconductor layer and a second nitride semiconductor layer having a greater band gap than that of the first nitride semiconductor layer are bonded together;
a second hetero-junction body in which a third nitride semiconductor layer formed on the first hetero-junction body and a fourth nitride semiconductor layer having a greater band gap than that of the third nitride semiconductor layer are bonded together;
a first electrode in Schottky contact with at least the fourth nitride semiconductor layer; and
a second electrode in ohmic contact with the first and second hetero-junction bodies,
wherein the first nitride semiconductor layer has such a thickness that an electron concentration in a 2-dimentional electron gas layer formed in the first nitride semiconductor layer is not reduced, or
the third nitride semiconductor layer has such a thickness that an electron concentration in a 2-dimentional electron gas layer formed in the third nitride semiconductor layer is not reduced.
2 . The semiconductor device of claim 1 , wherein
the thickness of the first nitride semiconductor layer or the third nitride semiconductor layer is equal to or greater than 80 nm.
3 . The semiconductor device of claim 1 , wherein
the third nitride semiconductor layer has, at an interface at which the third nitride semiconductor layer contacts the second nitride semiconductor layer, a first region doped with an n-impurity.
4 . The semiconductor device of claim 3 , wherein
the third nitride semiconductor layer has a second region formed between the first region and the fourth nitride semiconductor layer so as to contact the first region and doped with a p-impurity.
5 . The semiconductor device of claim 1 , wherein
the first electrode is a gate electrode,
the second electrode includes a source electrode formed in a region extending over the first and second hetero-junction bodies on one side of the gate electrode, and a drain electrode formed in a region extending over the first and second hetero-junction bodies on the other side of the gate electrode, and
the semiconductor device is operated as a field effect transistor.
6 . The semiconductor device of claim 5 , wherein
the first electrode is a first gate electrode,
a substrate configured to hold the first hetero-junction body is further provided,
the substrate is provided in a region of the semiconductor device opposite to the first gate electrode, and is formed with an opening through which part of the first hetero-junction body is exposed, and
a second gate electrode contacting at least the part of the first hetero-junction body exposed through the opening is formed on the substrate.
7 . The semiconductor device of claim 1 , wherein
the first electrode is an anode electrode,
the second electrode is a cathode electrode, and
the semiconductor device is operated as a Schottky barrier diode.
8 . The semiconductor device of claim 7 , wherein
the thickness of the third nitride semiconductor layer is equal to or less than 350 nm.