Semiconductor device

Abstract

In a semiconductor device in the present disclosure, a first nitride semiconductor layer has a two-dimensional electron gas channel in a vicinity of an interface with a second nitride semiconductor layer. In plan view, an electrode portion is provided between a first electrode and a second electrode with a space between the first electrode and the second electrode, and a space between the second electrode and the electrode portion is smaller than the space between the first electrode and the electrode portion. An energy barrier is provided in a junction surface between the electrode portion and the second nitride semiconductor layer, the energy barrier indicating a rectifying action in a forward direction from the electrode portion to the second nitride semiconductor layer, and a bandgap of the second nitride semiconductor layer is wider than a bandgap of the first nitride semiconductor layer.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a substrate;   a first nitride semiconductor layer provided on the substrate;   a second nitride semiconductor layer provided on the first nitride semiconductor layer;   a first electrode provided above a lower surface of the first nitride semiconductor layer and serving as a source electrode or an anode electrode;   a second electrode provided above the lower surface of the first semiconductor layer and serving as a drain electrode or a cathode electrode; and   an electrode portion provided above a lower surface of the second nitride semiconductor layer, wherein   the first nitride semiconductor layer has a two-dimensional electron gas channel in a vicinity of an interface with the second nitride semiconductor layer,   the first nitride semiconductor layer and the second nitride semiconductor layer form a semiconductor layer stacked body,   the electrode portion is disposed between the first electrode and the second electrode with a space between the first electrode and the second electrode, and a space between the second electrode and the electrode portion is smaller than a space between the first electrode and the electrode portion, in plan view, and   a junction surface between the electrode portion and the second nitride semiconductor layer has an energy barrier indicating a rectifying action in a forward direction from the electrode portion to the second nitride semiconductor layer,   a bandgap of the second nitride semiconductor layer is wider than a bandgap of the first nitride semiconductor layer,   the electrode portion has a potential substantially equal to a potential of the second electrode, and   the two-dimensional electron gas channel under the electrode portion is in a conductive state when a maximum operating voltage, which renders the first electrode positive, is applied between the first electrode and the second electrode.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein
 the electrode portion forms a Schottky contact with second nitride semiconductor layer.   
     
     
         3 . The semiconductor device according to  claim 1 , wherein
 the electrode portion is a third nitride semiconductor layer.   
     
     
         4 . The semiconductor device according to  claim 1 , wherein
 the electrode portion is an organic semiconductor layer.   
     
     
         5 . The semiconductor device according to  claim 1 , wherein
 the electrode portion is an oxide semiconductor layer.   
     
     
         6 . The semiconductor device according to  claim 1 , wherein
 the electrode portion has a p-conductivity.   
     
     
         7 . The semiconductor device according to  claim 1 , wherein
 an interlayer insulating film is formed to cover the second electrode,   the interlayer insulating film partially has an opening, and   a second electrode wiring line is formed in the opening and connected to the second electrode.   
     
     
         8 . The semiconductor device according to  claim 7 , wherein
 the second electrode is surrounded by the electrode portion, and   the opening is disposed at an intersecting point between the second electrode wiring line and the electrode portion.   
     
     
         9 . The semiconductor device according to  claim 7 , wherein
 the electrode portion has a plurality of island-shaped portions spaced apart from each other,   the opening is disposed above each of the plurality of island-shaped portions, and   the second electrode wiring line hangs over the plurality of island-shaped portions.   
     
     
         10 . The semiconductor device according to  claim 7 , wherein
 the second electrode wiring line is formed inside the electrode portion with respect to a direction toward the first electrode.   
     
     
         11 . The semiconductor device according to  claim 1 , wherein
 the electrode portion is in contact with the second electrode.   
     
     
         12 . The semiconductor device according to  claim 11 , wherein
 the electrode portion forms a Schottky junction with the second electrode.   
     
     
         13 . The semiconductor device according to  claim 1 , wherein
 the semiconductor layer stacked body partially serves as a high carrier concentration semiconductor layer,   a sheet carrier concentration of the high carrier concentration semiconductor layer is higher than a sheet carrier concentration of another portion of the semiconductor layer stacked body, and   the high carrier concentration semiconductor layer is provided at least in a region just under the electrode portion.   
     
     
         14 . The semiconductor device according to  claim 13 , wherein
 the second nitride semiconductor layer in the high carrier concentration semiconductor layer is thicker than the second nitride semiconductor layer in the semiconductor layer stacked body.   
     
     
         15 . The semiconductor device according to  claim 13 , wherein
 a bandgap of the second nitride semiconductor layer in the high carrier concentration semiconductor layer is wider than a bandgap of the second nitride semiconductor layer in the semiconductor layer stacked body.   
     
     
         16 . The semiconductor device according to  claim 13 , wherein
 an n-impurity concentration of the first nitride semiconductor layer in the higher carrier concentration semiconductor layer is higher than an n-impurity concentration of the first nitride semiconductor layer in the semiconductor layer stacked body.   
     
     
         17 . The semiconductor device according to  claim 1 , wherein
 the first electrode is an anode electrode,   the second electrode is a cathode electrode, and   the semiconductor device functions as a diode.   
     
     
         18 . The semiconductor device according to  claim 17 , wherein
 the anode electrode is formed on the semiconductor layer stacked body, or the substrate, and makes a Schottky contact with the semiconductor layer stacked body, and the semiconductor device functions as the diode.   
     
     
         19 . The semiconductor device according to  claim 1 , further comprising a gate electrode formed on the semiconductor layer stacked body and between the first electrode and the electrode portion with a space between the first electrode and the electrode portion, wherein
 the first electrode is a source electrode,   the second electrode is a drain electrode, and   the semiconductor device functions as a field effect transistor.   
     
     
         20 . The semiconductor device according to  claim 19 , wherein
 when a second voltage lower than a breakdown voltage of the semiconductor device is applied to a place between the source electrode and the drain electrode with a first voltage equal to or higher than a gate threshold voltage being applied to the gate electrode, a potential difference between the electrode portion and the second nitride semiconductor layer just under the electrode portion reaches a value equal to or greater than the energy barrier, and a current flows from the electrode portion to the source electrode.