Semiconductor device and method of manufacturing the same

Abstract

A semiconductor device includes a semiconductor substrate, and a P-well and an N-type drift region disposed in the semiconductor substrate. The P-well includes a lower well region and an upper well region disposed above the lower well region. The lower well region includes a first surface that is near the N-type drift region, and the upper well region includes a second surface that is near the N-type drift region. A distance from the first surface of the lower well region to the N-type drift region is greater than a distance from the second surface of the upper well region to the N-type drift region.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a semiconductor substrate;   a P-well and an N-type drift region disposed in the semiconductor substrate, wherein the P-well includes a lower well region and an upper well region disposed above the lower well region,   wherein the lower well region includes a first surface that is near the N-type drift region, and the upper well region includes a second surface that is near the N-type drift region, and   wherein a distance from the first surface of the lower well region to the N-type drift region is greater than a distance from the second surface of the upper well region to the N-type drift region.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the first surface of the lower well region is a sloped surface, and wherein a distance from an upper portion of the sloped surface to the N-type drift region is less than a distance from a lower portion of the sloped surface to the N-type drift region. 
     
     
         3 . The semiconductor device according to  claim 1 , wherein the lower well region is formed through an ion implantation process, and wherein an implantation angle of the ion implantation process is an acute angle. 
     
     
         4 . The semiconductor device according to  claim 1 , wherein the semiconductor device further comprises a source disposed in the P-well electrode, a drain disposed in the N-type drain drift region, and a gate disposed on the semiconductor substrate. 
     
     
         5 . The semiconductor device according to  claim 4 , wherein the semiconductor device further comprises a body electrode disposed in the P-well. 
     
     
         6 . A method of manufacturing a semiconductor device, comprising:
 forming an N-type drift region and a P-well in a semiconductor substrate, wherein forming the P-well further comprises:
 forming a mask layer on the semiconductor substrate; 
 performing a first ion implantation on the semiconductor substrate through the mask layer so as to form a lower well region, wherein an implantation angle of the first ion implantation process is an acute angle; 
 performing a second ion implantation on the semiconductor substrate through the mask layer so as to form an upper well region, wherein an implantation angle of the second ion implantation process is zero degree, wherein the upper well region is disposed above the lower well region, wherein the upper well region and the lower well region collectively constitute the P-well, wherein the lower well region includes a first surface that is near the N-type drift region, and the upper well region includes a second surface that is near the N-type drift region, and wherein a distance from the first surface of the lower well region to the N-type drift region is greater than a distance from the second surface of the upper well region to the N-type drift region; and 
 removing the mask layer.