Nitride-based semiconductor device with concave gate region

Abstract

In FET, a second nitride semiconductor layer is provided on a first nitride semiconductor layer, and a source electrode and a drain electrode are each provided to have at least a portion thereof in contact with the second nitride semiconductor layer. A concave portion is formed in the upper surface of the second nitride semiconductor layer to be located between the source electrode and the drain electrode. A gate electrode is provided over the concave portion to cover the opening of the concave portion.

1 - 18 . (canceled) 
     
     
         19 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   an insulating film in contact with a portion of the upper surface of the semiconductor multilayer and opened to expose the concave portion, wherein   the gate electrode has a portion thereof provided over the insulating film, and   a length of an extended portion of the gate electrode located over the semiconductor multilayer expanding toward the source electrode is different from a length of an extended portion of the gate electrode located over the semiconductor multilayer expanding toward the drain electrode.   
     
     
         20 . The semiconductor device of  claim 19 , wherein
 a length of an extended portion of the gate electrode located over the semiconductor multilayer is larger on a side with the drain electrode than on a side with the source electrode.   
     
     
         21 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   an insulating film in contact with a portion of the upper surface of the semiconductor multilayer and opened to expose the concave portion, wherein   the gate electrode has a portion thereof provided over the insulating film, and   an opening of the insulating film is larger than an opening of the concave portion.   
     
     
         22 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   an insulating film in contact with a portion of the upper surface of the semiconductor multilayer and opened to expose the concave portion, wherein   the gate electrode has a portion thereof provided over the insulating film,   a first hole and a second hole are formed in the second nitride-based compound semiconductor layer,   the source electrode is provided in the first hole, and   the drain electrode is provided in the second hole.   
     
     
         23 . The semiconductor device of  claim 22 , wherein
 the first hole and the second hole reach a two-dimensional electron gas layer located in a vicinity of an upper surface of the first nitride-based compound semiconductor layer.   
     
     
         24 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   an insulating film in contact with a portion of the upper surface of the semiconductor multilayer and opened to expose the concave portion, wherein   the gate electrode has a portion thereof provided over the insulating film, and   an etching stop layer is formed between the first nitride-based compound semiconductor layer and the second nitride-based compound semiconductor layer.   
     
     
         25 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   an insulating film in contact with a portion of the upper surface of the semiconductor multilayer and opened to expose the concave portion, wherein   the gate electrode has a portion thereof provided over the insulating film, and   an isolation region is positioned opposite to the gate electrode with respect to the drain electrode, and is positioned opposite to the gate electrode with respect to the source electrode.   
     
     
         26 . The semiconductor device of  claim 25 , wherein ions are implanted in the isolation region. 
     
     
         27 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   a p-type nitride-based compound semiconductor layer provided to cover the opening of the concave portion and to be located between the gate electrode and the semiconductor multilayer, wherein   the p-type nitride-based compound semiconductor layer works as a part of a terminal for controlling a current between the source and the drain by applying a voltage,   a film thickness of a portion of the p-type nitride-based compound semiconductor layer located over a bottom surface of the concave portion is larger than a film thickness of a portion of the p-type nitride-based compound semiconductor layer located on the upper surface of the semiconductor multilayer, and   a thickness of a part of the p-type nitride-based compound semiconductor layer located under the source region is smaller than a thickness of a part of the p-type nitride-based compound semiconductor layer located outside a region in which the source electrode is formed.   
     
     
         28 . A semiconductor device comprising:
 a substrate;   a semiconductor multilayer having a first nitride-based compound semiconductor layer provided over the substrate and a second nitride-based compound semiconductor layer provided over the first nitride-based compound semiconductor layer to have a band gap larger than that of the first nitride-based compound semiconductor layer;   a source electrode and a drain electrode each provided to have at least a portion thereof in contact with the semiconductor multilayer;   a concave portion provided on an upper surface of the semiconductor multilayer to be located between the source electrode and the drain electrode, and concaved in a thickness direction of the semiconductor multilayer;   a gate electrode provided over the concave portion to cover an opening of the concave portion; and   a p-type nitride-based compound semiconductor layer provided to cover the opening of the concave portion and to be located between the gate electrode and the semiconductor multilayer, wherein   the p-type nitride-based compound semiconductor layer works as a part of a terminal for controlling a current between the source and the drain by applying a voltage,   a film thickness of a portion of the p-type nitride-based compound semiconductor layer located over a bottom surface of the concave portion is larger than a film thickness of a portion of the p-type nitride-based compound semiconductor layer located on the upper surface of the semiconductor multilayer, and   an isolation region is positioned opposite to the gate electrode with respect to the drain electrode, and is positioned opposite to the gate electrode with respect to the source electrode.   
     
     
         29 . The semiconductor device of  claim 28 , wherein ions are implanted in the isolation region.