Semiconductor device and production method thereof

Abstract

A semiconductor device that makes it possible to restrain the increase of the junction capacitance and others while preventing the punch-through and others accompanying the scale reduction, and a production method thereof are obtained. The semiconductor device includes source and drain regions of first conductivity type disposed to sandwich a channel region, and a pair of pocket injection regions of second conductivity type that cover only a neighborhood of side surface parts of the source and drain regions on the channel region side and respectively form a junction only between the neighborhood of the side surface parts and the pocket injection regions.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 source and drain regions of first conductivity type disposed to sandwich a channel region located in a surface part of a semiconductor layer, and    a pair of pocket injection regions of second conductivity type that cover only a neighborhood of respective side surface parts of said source and drain regions on said channel region side and form a junction only between the neighborhood of said side surface parts and the pocket injection regions.    
     
     
         2 . The semiconductor device as set forth in  claim 1 , wherein said source and drain regions include source extension and drain extension regions of first conductivity type that extend towards said channel region, and 
 each of said pocket injection regions covers a side surface and a bottom surface of the source extension and drain extension regions on said channel region side to form a junction.    
     
     
         3 . The semiconductor device as set forth in  claim 2 , wherein the junction between said source and drain regions and said pocket injection regions is located successively to the junction between said source extension and drain extension regions and said pocket injection regions.  
     
     
         4 . The semiconductor device as set forth in  claim 1 , further comprising semiconductor compound layers disposed on said source and drain regions and respectively at positions elevated above said channel region.  
     
     
         5 . The semiconductor device as set forth in  claim 4 , wherein said semiconductor compound layers disposed at the elevated positions are made of metal silicide.  
     
     
         6 . The semiconductor device as set forth in  claim 1 , further comprising metal films deposited on said source and drain regions and respectively at positions elevated above said channel region.  
     
     
         7 . The semiconductor device as set forth in  claim 1 , wherein an impurity element heavier than an element constituting said semiconductor is injected into upper regions of said source and drain regions.  
     
     
         8 . A method of producing a semiconductor device, comprising the steps of: 
 forming a gate electrode on a channel region formed from a surface of a semiconductor layer to a predetermined depth;    forming a pair of side wall spacers on both sides of said gate electrode;    forming semiconductor layers, each being elevated above said channel region, on regions which is outside said pair of side wall spacers and in which source and drain regions of first conductivity type are to be formed;    removing said pair of side wall spacers; and    forming a pair of pocket injection regions of second conductivity type by introducing, after said side wall spacers are removed, an impurity of second conductivity type below a region where said side wall spacers were formed, said pair of pocket injection regions respectively covering only a neighborhood of respective side surface parts, on said channel region side, of the region where said source and drain regions are to be formed, so as to form a junction only between said neighborhood of the side surface parts and said pocket injection region.    
     
     
         9 . The method of producing a semiconductor device as set forth in  claim 8 , wherein an impurity of second conductivity type is injected into a region below the region where said side wall spacers were formed, using said gate electrode and said elevated semiconductor layers as a mask in forming said pocket injection regions.  
     
     
         10 . The method of producing a semiconductor device as set forth in  claim 8 , further comprising a step of respectively forming source extension and drain extension regions of first conductivity type that extend from the region where said source and drain regions are to be formed, by introducing an impurity of first conductivity type into a region which is in contact with a surface of said pocket injection regions on a side of the region where said source and drain regions are to be formed, successively after said pocket injection regions are formed.  
     
     
         11 . The method of producing a semiconductor device as set forth in  claim 10 , further comprising, after the step of respectively forming said source extension and drain extension regions, a step of forming side wall spacers again in the region where said side wall spacers were formed, thereafter a step of introducing an impurity of first conductivity type into the region where said source and drain regions are to be formed, so as to form the source and drain regions, and a step of turning said elevated semiconductor layers into metal silicide.  
     
     
         12 . The method of producing a semiconductor device as set forth in  claim 10 , further comprising, between the step of forming said elevated semiconductor layers and the step of removing said side wall spacers, a step of introducing an impurity of first conductivity type through said elevated semiconductor layers into a lower region to form the source and drain regions.  
     
     
         13 . The method of producing a semiconductor device as set forth in  claim 12 , further comprising, after the steps of forming said source and drain regions, removing said side wall spacers, and respectively forming said pocket injection regions and said source extension and drain extension regions, a step of forming side wall spacers again in a region where said side wall spacers were formed and a step of turning an upper part of said elevated semiconductor layers into metal silicide.  
     
     
         14 . The method of producing a semiconductor device as set forth in  claim 12 , further comprising, after the step of forming said source and drain regions and before the step of removing said side wall spacers, a step of turning said elevated semiconductor layers into metal silicide.  
     
     
         15 . The method of producing a semiconductor device as set forth in  claim 8 , wherein the step of forming said side wall spacers comprises a step of forming the side wall spacers so as to form a two-layer structure having a lower layer of silicon oxide film and an upper layer of silicon nitride film.  
     
     
         16 . The method of producing a semiconductor device as set forth in  claim 8 , wherein, in the step of forming said pocket injection regions, an impurity of second conductivity type is introduced by ion injection method, and its injection angle θ from the vertical direction is set to be not larger than tan −1 (Ls/Te), where 
 Ls=width of the removed side walls, and  
 Te=height by which the source and drain regions are elevated from the channel region.  
 
     
     
         17 . The method of producing a semiconductor device as set forth in  claim 8 , wherein, after said side wall spacers are removed, a deposition layer containing an impurity of second conductivity type is formed and then a heat treatment is carried out so that said impurity of second conductivity type is introduced by thermal diffusion from the deposition layer containing said impurity of second conductivity type, thereby to form said pocket injection regions.  
     
     
         18 . The method of producing a semiconductor device as set forth in  claim 8 , wherein, instead of the step of forming the semiconductor layers to be elevated above said channel region, either one of an oxide film or a nitride film of said semiconductor is formed to be elevated above said channel region by either one of a thermal oxidation method and a thermal nitriding method.  
     
     
         19 . The method of producing a semiconductor device as set forth in  claim 8 , wherein, instead of the step of forming the semiconductor layers to be elevated above said channel region, a metal layer is formed to be elevated above said channel region.  
     
     
         20 . The method of producing a semiconductor device as set forth in  claim 8 , wherein, instead of the step of forming the semiconductor layers to be elevated above said channel region, an impurity element heavier than an element constituting said semiconductor is introduced into an upper part of said source and drain regions.