Semiconductor device

A semiconductor device, comprising:

• a first nitride semiconductor layer;
• a second nitride semiconductor layer arranged over the first nitride semiconductor layer;
• a third nitride semiconductor layer arranged over the second nitride semiconductor layer, and in a part of a formation region of the second nitride semiconductor layer;
• and
• a fourth nitride semiconductor layer arranged between the third nitride semiconductor layer and the second nitride semiconductor layer, and partially in an overlapping region of the third nitride semiconductor layer and the second nitride semiconductor layer,
• wherein the first nitride semiconductor layer is larger in band gap than the second nitride semiconductor layer, and is of a first conductivity type,
• wherein the third nitride semiconductor layer is larger in band gap than the second nitride semiconductor layer, and is of a second conductivity type which is the opposite conductivity type to the first conductivity type,
• wherein the fourth nitride semiconductor layer is larger in band gap than the third nitride semiconductor layer.
• wherein an overlapping region of the third nitride semiconductor layer and the second nitride semiconductor layer is in a line shape, and
• wherein the fourth nitride semiconductor layer is also arranged on each opposite side of the overlapping region.

A semiconductor device, comprising:

• a first nitride semiconductor layer;
• a second nitride semiconductor layer arranged over the first nitride semiconductor layer;
• a third nitride semiconductor layer arranged over the second nitride semiconductor layer;
• and
• a first film and a second film arranged between the third nitride semiconductor layer and the second nitride semiconductor layer, and formed of a fourth nitride semiconductor layer,
• wherein the first film is arranged partially in a first region,
• wherein the second film is arranged in a second region situated on each opposite side of the first region,
• wherein the first nitride semiconductor layer is larger in band gap than the second nitride semiconductor layer, and is of a first conductivity type,
• wherein the third nitride semiconductor layer is larger in band gap than the second nitride semiconductor layer, and is of a second conductivity type which is the opposite conductivity type to the first conductivity type, and
• wherein the fourth nitride semiconductor layer is larger in band gap than the third nitride semiconductor layer.