Semiconductor device

Abstract

The present invention makes it possible, in a manufacturing process of a semiconductor device, to inhibit: impurities from diffusing from a substrate to a semiconductor layer; and the withstand voltage of a transistor from deteriorating. In the present invention, a first electrically conductive type epitaxial layer is formed over a first electrically conductive type base substrate. The impurity concentration of the epitaxial layer is lower than that of the base substrate. A second electrically conductive type first embedded layer and a second electrically conductive type second embedded layer are formed in the epitaxial layer. The second embedded layer is deeper than the first embedded layer, is kept away from the first embedded layer, and has an impurity concentration lower than the first embedded layer. A transistor is further formed in the epitaxial layer.

What is claimed is: 
     
         1 . A semiconductor device having: a first electrically conductive type base substrate; a first electrically conductive type semiconductor layer being formed over the base substrate and having an impurity concentration lower than the base substrate; a second electrically conductive type first embedded layer formed in the semiconductor layer; a second embedded layer being formed in the semiconductor layer, being deeper than the first embedded layer, being kept away from the first embedded layer, and having an impurity concentration lower than the first embedded layer; and transistors formed in the semiconductor layer. 
     
     
         2 . A semiconductor device according to  claim 1 ,
 wherein the semiconductor device has trenches being formed in the semiconductor layer and surrounding the transistors and an insulating film embedded into the trenches; and the bottom faces of the trenches are located at positions shallower than the second embodiment layer.   
     
     
         3 . A semiconductor device according to  claim 1 ,
 wherein the semiconductor device has a hole formed in the semiconductor layer, an insulating layer formed over the side face of the hole, and a conductor embedded into the hole; and the bottom face of the hole is deeper than the second embedded layer.   
     
     
         4 . A semiconductor device according to  claim 3 ,
 wherein the semiconductor device has a first electrically conductive type region being formed in the semiconductor layer, being located at the bottom part of the hole, and having an impurity concentration higher than the semiconductor layer.   
     
     
         5 . A semiconductor device according to  claim 1 ,
 wherein P is introduced into the second embedded layer and B is introduced into the base substrate.