Semiconductor device
View Patent ↗A semiconductor device includes a field effect transistor that has a first nitride semiconductor layer and a second nitride semiconductor layer larger in bandgap than the first nitride semiconductor layer formed on a substrate in this order and a gate electrode, a source electrode, and a drain electrode, and uses two-dimensional electron gas formed at the interface between the first and second nitride semiconductor layers as the channel. The field effect transistor further has a p-type nitride semiconductor layer formed between the gate electrode and the drain electrode and electrically connected to the drain electrode.
1. A semiconductor device comprising a field effect transistor, the transistor having a first nitride semiconductor layer formed on a substrate, a second nitride semiconductor layer larger in bandgap than the first nitride semiconductor layer formed on the first nitride semiconductor layer, a gate electrode formed on the second nitride semiconductor layer, and a source electrode and a drain electrode formed to sandwich the gate electrode each being in contact with at least the second nitride semiconductor layer, the transistor using two-dimensional electron gas formed at an interface between the first nitride semiconductor layer and the second nitride semiconductor layer as a channel,
wherein the field effect transistor further has a p-type nitride semiconductor layer formed on the second nitride semiconductor layer at a position between the gate electrode and the drain electrode and electrically connected to the drain electrode, and
an n-type nitride semiconductor layer is formed between the p-type nitride semiconductor layer and the first nitride semiconductor layer.
2. The semiconductor device of claim 1 , wherein the n-type nitride semiconductor layer is formed in a region inside the second nitride semiconductor layer or on the second nitride semiconductor layer located right under the p-type nitride semiconductor layer.
3. The semiconductor device of claim 1 , wherein
the n-type nitride semiconductor layer is formed inside the second nitride semiconductor layer, and
the n-type impurity concentration of the n-type nitride semiconductor layer is higher than the n-type impurity concentration of the second nitride semiconductor layer excluding the region of the n-type nitride semiconductor layer.
4. The semiconductor device of claim 1 , wherein the hole carrier concentration of the p-type nitride semiconductor layer is larger than the electron carrier concentration of the n-type nitride semiconductor layer.
5. The semiconductor device of claim 1 , wherein the n-type nitride semiconductor layer is formed inside the second nitride semiconductor layer, extending from underneath the p-type nitride semiconductor layer to a position in contact with the source electrode and to a position in contact with the drain electrode.
6. The semiconductor device of claim 1 , wherein the field effect transistor further has an electrode connecting the p-type nitride semiconductor layer to the drain electrode.
7. The semiconductor device of claim 1 , wherein
the p-type nitride semiconductor layer is placed apart from the drain electrode, and
the distance between the p-type nitride semiconductor layer and the gate electrode is larger than the distance between the p-type nitride semiconductor layer and the drain electrode.
8. The semiconductor device of claim 1 , wherein
the first nitride semiconductor layer is made of GaN, and
the second nitride semiconductor layer is made of AlGaN.
9. The semiconductor device of claim 1 , wherein the p-type nitride semiconductor layer is made of p-type GaN.
10. The semiconductor device of claim 1 , wherein the p-type impurity concentrations of the first nitride semiconductor layer and the second nitride semiconductor layer are both lower than the p-type impurity concentration of the p-type nitride semiconductor layer.