NITRIDE SEMICONDUCTOR DEVICE
A nitride semiconductor device includes: a first semiconductor layer made of first nitride semiconductor; a second semiconductor layer formed on a principal surface of the first semiconductor layer and made of second nitride semiconductor having a bandgap wider than that of the first nitride semiconductor; a control layer selectively formed on, or above, an upper portion of the second semiconductor layer and made of third nitride semiconductor having a p-type conductivity; source and drain electrodes formed on the second semiconductor layer at respective sides of the control layer; a gate electrode formed on the control layer; and a fourth semiconductor layer formed on a surface of the first semiconductor layer opposite to the principal surface, having a potential barrier in a valence band with respect to the first nitride semiconductor and made of fourth nitride semiconductor containing aluminum.
1 - 6 . (canceled)
7 . A nitride semiconductor device, comprising:
a first semiconductor layer made of first nitride semiconductor;
a second semiconductor layer formed on a principal surface of the first semiconductor layer and made of second nitride semiconductor having a bandgap wider than that of the first nitride semiconductor;
a control layer selectively formed on an upper portion of the second semiconductor layer and made of third nitride semiconductor having a p-type conductivity;
source and drain electrodes formed on the second semiconductor layer at respective sides of the control layer;
a fourth semiconductor layer formed on a surface of the first semiconductor layer opposite to the principal surface; and
a passivation film for covering at least a side surface of the control layer,
wherein a thickness of the control layer is greater than a thickness of the second semiconductor layer.
8 . The nitride semiconductor device of claim 7 , wherein the passivation film is a silicon nitride film.