Nitride semiconductor device and method for manufacturing same

Abstract

According to one embodiment, a nitride semiconductor device includes a first semiconductor, a second semiconductor layer, a third semiconductor layer, a fourth semiconductor layer, a first electrode, a second electrode and a third electrode. The first, second and fourth semiconductor layers include a nitride semiconductor. The second semiconductor layer is provided on the first semiconductor layer, has a band gap not less than that of the first semiconductor layer. The third semiconductor layer is provided on the second semiconductor layer. The third semiconductor layer is GaN. The fourth semiconductor layer is provided on the third semiconductor layer to have an interspace on a part of the third semiconductor layer, has a band gap not less than that of the second semiconductor layer. The first electrode is provided on a portion of the third semiconductor layer. The fourth semiconductor layer is not provided on the portion.

1 - 7 . (canceled) 
     
     
         8 . A nitride semiconductor device comprising:
 a first semiconductor layer including a nitride semiconductor;   a second semiconductor layer provided on the first semiconductor layer, having a band gap not less than a band gap of the first semiconductor layer, and including a nitride semiconductor;   a third semiconductor layer provided on a part of the second semiconductor layer, the third semiconductor layer being GaN;   fourth semiconductor layers provided on both sides of the third semiconductor layer on the second semiconductor layer, having a band gap not less than a band gap of the second semiconductor layer, and including a nitride semiconductor;   a first electrode provided above a portion of the third semiconductor layer, the fourth semiconductor layers being not provided on the portion;   a second electrode provided on one side of the first electrode on the fourth semiconductor layers and connected to the fourth semiconductor layers by ohmic junction; and   a third electrode provided on another side of the first electrode on the fourth semiconductor layers and connected to the fourth semiconductor layers by ohmic junction.   
     
     
         9 . The device according to  claim 8 , wherein
 the first semiconductor layer includes Al X Ga 1-X N (0≦X≦1),   the second semiconductor layer includes Al Y Ga 1-Y N (0≦Y≦ 1 , X≦Y), and   the fourth semiconductor layer includes Al Z Ga 1-Z N (0≦Z≦ 1 , X≦Z).   
     
     
         10 . The device according to  claim 8 , further comprising a fifth semiconductor layer provided between the second semiconductor layer and the fourth semiconductor layer, and including an n-type nitride semiconductor. 
     
     
         11 . The device according to  claim 10 , wherein the fifth semiconductor layer includes Al m Ga 1-m N (0≦m≦1). 
     
     
         12 . The device according to  claim 8 , further comprising an insulating layer provided between the first electrode and the third semiconductor layer. 
     
     
         13 . The device according to  claim 8 , wherein the first electrode is connected to the third semiconductor layer by Schottky junction. 
     
     
         14 . The device according to  claim 8 , wherein the first semiconductor layer includes a channel in a normally OFF transistor. 
     
     
         15 . A method for manufacturing a nitride semiconductor device comprising:
 forming a first semiconductor layer including a nitride semiconductor, a second semiconductor layer provided on the first semiconductor layer, and a third semiconductor layer provided on the second semiconductor layer on a support substrate, the second semiconductor layer having a band gap not less than a band gap of the first semiconductor layer, and including a nitride semiconductor, the third semiconductor layer being GaN;   forming a fourth semiconductor layer provided on the third semiconductor layer to have an interspace on a part of the third semiconductor layer, having a band gap not less than a band gap of the second semiconductor layer, and including a nitride semiconductor; and   forming a first electrode above a portion of the third semiconductor layer, the fourth semiconductor layer being not formed on the portion, and forming a second electrode on one side of the first electrode on the fourth semiconductor layer and a third electrode on another side of the first electrode on the fourth semiconductor layer.   
     
     
         16 . A method for manufacturing a nitride semiconductor device comprising:
 forming a first semiconductor layer including a nitride semiconductor, a second semiconductor layer provided on the first semiconductor layer, and a third semiconductor layer provided on a part of the second semiconductor layer on a support substrate, the second semiconductor layer having a band gap not less than a band gap of the first semiconductor layer, and including a nitride semiconductor, the third semiconductor layer being GaN;   forming fourth semiconductor layers having a band gap not less than a band gap of the second semiconductor layer and including a nitride semiconductor on both sides of the third semiconductor layer on the second semiconductor layer; and   forming a first electrode above a portion of the third semiconductor layer, the fourth semiconductor layers being not formed on the portion, and forming a second electrode on one side of the first electrode on the fourth semiconductor layers and a third electrode on another side of the first electrode on the fourth semiconductor layers.