Nitride semiconductor device

Abstract

A nitride semiconductor device is provided that prevents development of cracks, that has nitride semiconductor thin films with uniform thicknesses and good growth surface flatness, and is thus consistent in characteristics, and that can be fabricated at a satisfactory yield. In this nitride semiconductor device, the nitride semiconductor thin films are grown on a substrate having an off-angle between a direction normal to the surface of ridges and the crystal direction <0001>. This helps either reduce or intentionally promote diffusion or movement of the atoms or molecules of a source material of the nitride semiconductor thin films through migration thereof. As a result, a nitride semiconductor growth layer with good surface flatness can be formed, and thus a nitride semiconductor device with satisfactory characteristics can be obtained.

What is claimed is: 
     
         1 . A nitride semiconductor device comprising:
 a processed substrate formed by forming a trench as a concave area on a surface of a nitride semiconductor substrate or on a surface of a nitride semiconductor layer formed on a substrate other than a nitride semiconductor substrate, and   a nitride semiconductor multiple-layer film composed of multiple films of nitride semiconductors including a nitride semiconductor primer layer formed first on the processed surface,   wherein the nitride semiconductor primer layer is a compound containing GaN.   
     
     
         2 . The nitride semiconductor device of  claim 1 ,
 wherein a layer thickness of the nitride semiconductor primer layer is 0.5 μm or less.   
     
     
         3 . The nitride semiconductor device of  claim 1 ,
 wherein a ratio of a layer thickness of the nitride semiconductor primer layer to a total layer thickness of the nitride semiconductor multiple-layer film is 15% or less.   
     
     
         4 . The nitride semiconductor device of  claim 1 ,
 wherein an angle between a line normal to a top-end portion of a side wall surface of the trench and a line normal to a surface elsewhere than in the trench is 60° or larger.   
     
     
         5 . The nitride semiconductor device of  claim 1 ,
 wherein a depth of the trench is 2 μm or more but 20 μm or less.   
     
     
         6 . The nitride semiconductor device of  claim 1 ,
 wherein a width of the trench is 1 μm or more.   
     
     
         7 . The nitride semiconductor device of  claim 1 ,
 wherein a period of the trench is 0.1 mm or more but 4 mm or less.   
     
     
         8 . A nitride semiconductor device comprising:
 a processed substrate formed by forming a trench as a concave area on a surface of a nitride semiconductor substrate or on a surface of a nitride semiconductor layer formed on a substrate other than a nitride semiconductor substrate, and   a nitride semiconductor multiple-layer film composed of multiple films of nitride semiconductors including a nitride semiconductor primer layer formed first on the processed surface,   wherein the nitride semiconductor primer layer is a compound containing GaN, and a total layer thickness of the nitride semiconductor multiple-layer film is 4 μm or less.   
     
     
         9 . The nitride semiconductor device of  claim 8 ,
 wherein a depth of the trench is 1 μm or more but 20 μm or less.   
     
     
         10 . The nitride semiconductor device of  claim 8 ,
 wherein a width of the trench is 1 μm or more.