Semiconductor device

Abstract

A semiconductor device, which is capable of improving isolation property of an isolation structure using STI without increasing impurity concentrations of wells, includes a well isolation structure in form of a shallow trench formed on the boundary between first and second wells opposite in conductivity type and adjacent to each other. When a first device region formed in the first well and a second device region formed in the second well are opposed at opposite sides of the well isolation structure, they are disposed at a first width (well isolation distance) than the second width when they are not opposed to each other. One of the device regions may be a dummy region which does not function as a circuit. In this configuration, angle of STI side walls is steeper, and STI width can be made smaller.

1 . (Cancelled)  
     
     
         2 . A semiconductor device comprising: 
 first and second wells opposite in conductivity type and adjacent to each other;    a well isolation structure in form of a shallow trench formed on the boundary of said first and second wells, said well isolation structure having a first width and a second width larger than the first isolation width;    a first device region provided in said first well; and    a second device region provided in said second well,    wherein said first and second device regions are provided so as to be opposed at said first width of said well isolation structure: wherein said first and second device regions do not meet facing at said second width of said well isolation structure; and wherein one of said opposed device regions is a dummy device region unnecessary for an actual circuit, and has a width at least equal to that of the other device region.    
     
     
         3 . The semiconductor device according to  claim 2 , wherein said dummy device region has the same conductivity type as that of the well in which it is formed.  
     
     
         4 . The semiconductor device according to  claim 2 , wherein said dummy device region has the opposite conductivity type from that of the well in which it is formed.  
     
     
         5 . A semiconductor device comprising: 
 first and second wells opposite in conductivity type and adjacent to each other;    a well isolation structure in form of a shallow trench formed on the boundary of said first and second wells, said well isolation structure having a first width and a second width larger than the first isolation width;    a first device region provided in said first well; and    a second device region provided in said second well,    wherein said first and second device regions are provided so as to be opposed at said first width of said well isolation structure; wherein said first and second device regions do not meet facing at said second width of said well isolation structure; and wherein when both of said device regions are not equal in width and at least one of said opposed device regions requires a fine device isolation structure, the other device region has a width capable of confronting the former device region over the full width of the former device region.    
     
     
         6 . The semiconductor device according to  claim 5 , wherein said other device region includes a dummy device region provided to at least one end of the other device region, said dummy device region ensuring necessary confronting length.  
     
     
         7 . The semiconductor device according to  claim 6 , wherein the conductivity of the dummy device region is the same as the conductivity of the other device region.  
     
     
         8 - 15 . (Cancelled)