Semiconductor device and method of making including cap layer and nitride semiconductor layer

Abstract

To enhance the reliability of the semiconductor device using a nitride semiconductor. A channel layer is formed over a substrate, a barrier layer is formed over the channel layer, a cap layer is formed over the barrier layer, and a gate electrode is formed over the cap layer. In addition, a nitride semiconductor layer is formed in a region where the cap layer over the barrier layer is not formed, and a source electrode and a drain electrode are formed over the nitride semiconductor layer. The cap layer is a p-type semiconductor layer, and the nitride semiconductor layer includes the same type of material as the cap layer and is in an intrinsic state or an n-type state.

What is claimed is: 
     
         1 . A manufacturing method of a semiconductor device having a field effect transistor, comprising the steps of:
 (a) providing a structure having a substrate, a channel layer being formed over the substrate and including a nitride semiconductor, a first nitride semiconductor layer formed over the channel layer, and a second nitride semiconductor layer formed over the first nitride semiconductor layer;   (b) forming, after step (a), a first metal layer including titanium or tantalum over the second nitride semiconductor layer excluding a first region;   (c) forming, after step (b), a metal nitride layer by causing the first metal layer and the second nitride semiconductor layer to react by thermal treatment;   (d) removing, after step (c), the metal nitride layer by wet etching, and leaving the second nitride semiconductor layer of the first region; and   (e) forming, after step (d), a gate electrode over the second nitride semiconductor layer remaining in the first region.   
     
     
         2 . The manufacturing method of the semiconductor device according to  claim 1 ,
 wherein the first nitride semiconductor layer is an aluminum gallium nitride layer.   
     
     
         3 . The manufacturing method of the semiconductor device according to  claim 2 ,
 wherein the second nitride semiconductor layer is a gallium nitride layer.   
     
     
         4 . The manufacturing method of the semiconductor device according to  claim 3 ,
 Wherein, in a region where the first metal layer is formed in step (b), a lower part of the second nitride semiconductor layer remains, in step (d), over the first nitride semiconductor layer.   
     
     
         5 . The manufacturing method of the semiconductor device according to  claim 4 , further comprising:
 (f) a step of forming, after step (d), a source electrode and a drain electrode over the lower part.   
     
     
         6 . The manufacturing method of the semiconductor device according to  claim 5 ,
 wherein, in step (b), a stacked metal film having the first metal layer at the bottom layer is formed over the second nitride semiconductor layer excluding the first region.   
     
     
         7 . The manufacturing method of the semiconductor device according to  claim 3 ,
 wherein the second nitride semiconductor layer in the structure provided in step (a) is a p-type gallium nitride layer.   
     
     
         8 . The manufacturing method of the semiconductor device according to  claim 3 ,
 wherein the second nitride semiconductor layer in the structure provided in step (a) is a stacked layer film of a first gallium nitride layer in an intrinsic state and a second p-type gallium nitride layer formed over the first layer gallium nitride.   
     
     
         9 . The manufacturing method of the semiconductor device according to  claim 3 ,
 wherein the second nitride semiconductor layer in the structure provided in step (a) is a first gallium nitride layer in an intrinsic state.