METHOD OF MANUFACTURING A SEMICONDUCTOR DEVICE AND THE SEMICONDUCTOR DEVICE
Characteristics of a high electron mobility transistor are improved. A stack having an n-type contact layer (n-type AlGaN layer), an electron supply layer (undoped AlGaN layer), and a channel layer (undoped GaN layer) is formed in a growth mode over a Ga plane parallel with a [0001] crystal axis direction. Then, after turning the stack upside down so that the n-type contact layer (n-type AlGaN layer) is situated to the upper surface and forming a trench, a gate electrode is formed by way of a gate insulation film. By stacking the channel layer (undoped GaN layer) and the electron supply layer (undoped AlGaN layer) successively in a [000-1] direction, (1) normally off operation and (2) increase of withstanding voltage can easily be compatible with each other.
1 . A method of manufacturing a semiconductor device including the steps of:
(a) epitaxially growing a second nitride semiconductor layer over a first nitride semiconductor layer in a [0001] direction, thereby forming a stack comprising the first nitride semiconductor layer and the second nitride semiconductor layer, and
(b) disposing the stack such that the [000-1] direction of the stack becomes upward and forming a gate electrode on the side of the first nitride semiconductor layer, in which
the first nitride semiconductor layer has a band gap larger than a band gap of the second nitride semiconductor.
2 . The method of manufacturing the semiconductor device according to claim 1 ,
wherein the step (a) includes the step of:
(a1) forming the first nitride semiconductor layer over a first substrate,
(a2) epitaxially growing the second nitride semiconductor layer over the first nitride semiconductor layer in the [0001] direction, thereby forming the stack comprising the first nitride semiconductor layer and the second nitride semiconductor layer,
(a3) bonding a second substrate over the second nitride semiconductor layer, and
(a4) peeling the first substrate from the first nitride semiconductor layer, and
wherein the step (b) is a step of
disposing the stack such that the second substrate is situated below and forming the gate electrode on the side of the first nitride semiconductor layer.
3 . The method of manufacturing the semiconductor device according to claim 2 , wherein
the first nitride semiconductor layer has a first layer and a second layer, and
the step (a1) is a step of forming a first n-type layer over the first substrate and then forming the second layer over the first layer, and
the step (b) is a step of forming a trench passing through the first layer and then forming the gate electrode over the second layer exposed at the bottom in the trench.
4 . The method of manufacturing the semiconductor device according to claim 3 , wherein
the step (b) is a step of forming the gate electrode by way of a gate insulation film over the second layer.
5 . The method of manufacturing the semiconductor device according to claim 2 , wherein
the step (a3) is a step of bonding the second substrate by way of a bonding layer over the second nitride semiconductor layer.
6 . The method of manufacturing the semiconductor device according to claim 3 , wherein
the step (a2) has a step of further forming a third nitride semiconductor layer having an opening over the second nitride semiconductor layer.
7 . The method of manufacturing the semiconductor device according to claim 2 , wherein
the step (b) is a step of forming an n-type semiconductor layer by ion implantation in a region excluding a first region over the first nitride semiconductor layer and then forming the gate electrode over the first region.
8 . The method of manufacturing the semiconductor device according to claim 7 , wherein
the step (b) is a step of forming the gate electrode by way of a gate insulation film over the first region.
9 . The method of manufacturing the semiconductor device according to claim 7 , wherein
the step (a2) has a step of further forming a third nitride semiconductor layer having an opening over the second nitride semiconductor layer.
10 . A semiconductor device including:
a first nitride semiconductor layer formed over a substrate,
a second nitride semiconductor layer formed over the first nitride semiconductor layer and having a band gap larger than a band gap of the first nitride semiconductor layer,
a gate electrode disposed over the second nitride semiconductor layer,
a first electrode disposed on at least one side of the gate electrode in a portion over the second nitride semiconductor layer, and
a first semiconductor region containing impurities formed in one of the second nitride semiconductor layer and the first nitride semiconductor layer on both sides of the gate electrode, in which
a crystal axis direction from the first nitride semiconductor layer to the second nitride semiconductor layer in a stacked portion of the first nitride semiconductor layer and the second nitride semiconductor layer is a [000-1] direction.
11 . The semiconductor device according to claim 10 , wherein
the first semiconductor region is an n-type region.
12 . The semiconductor device according to claim 10 , wherein
a bonding layer is provided between the substrate and the first nitride semiconductor layer.
13 . The semiconductor device according to claim 11 , wherein
the first nitride semiconductor layer, the second nitride semiconductor layer, and the first semiconductor region are stacked orderly from below over the substrate,
the gate electrode is disposed by way of a gate insulation film over the second nitride semiconductor layer,
the first electrode is disposed by way of the first semiconductor region to one side of the gate electrodes in a portion over the second nitride semiconductor layer, and
a second electrode is disposed by way of the first semiconductor region on the other side of the gate electrode in a portion over the second nitride semiconductor layer.
14 . The semiconductor device according to claim 13 , wherein
the device has a trench passing through the first semiconductor region and reaching as far as the second nitride semiconductor layer, and
the gate electrode is disposed by way of the gate insulation film inside the trench.
15 . The semiconductor device according to claim 10 , wherein
the first nitride semiconductor layer, the second nitride semiconductor layer, and the first semiconductor region are stacked orderly from below over the substrate and
a second electrode connected electrically with the first nitride semiconductor layer is provided below the first nitride semiconductor layer.
16 . The semiconductor device according to claim 15 , wherein
the device has a trench passing through the first semiconductor region and reaching as far as the second nitride semiconductor layer, and
the gate electrode is disposed by way of a gate insulation film inside the trench.
17 . The semiconductor device according to claim 15 , wherein
a second semiconductor region having an opening is provided in a layer below the first nitride semiconductor layer.
18 . The semiconductor device according to claim 17 , wherein
the second semiconductor region is a p-type region.