Solid state image sensing device having pixels provided with barrier layer underneath transistor regions and camera using said device

Abstract

A solid-state image sensing device includes a plurality of pixels. Each pixel has a photodiode, a first transistor, and a second transistor. The photodiode is constituted by a first-conductivity-type semiconductor region and a second-conductivity-type semiconductor region. The first and second conductivity types are opposite to each other. The first transistor has a first-conductivity-type drain region formed in the second-conductivity-type semiconductor region to transfer signal charge to the drain region. The second transistor has a source region and a drain region which are formed in the second-conductivity-type semiconductor region and which have the first conductivity type. At least one second-conductivity-type potential barrier is provided under the drain region of the first transistor and the source region and/or the drain region of the second transistor.

1 . A solid-state image sensing device having a plurality of pixels, each pixel comprising: 
 a photodiode that is constituted by a semiconductor region having a first conductivity type and a semiconductor region having a second conductivity type to generate signal charge, the first conductivity type and the second conductivity type being opposite to each other;    a first transistor that has a drain region formed in the second-conductivity-type semiconductor region to transfer the signal charge to the drain region, the drain region having the first conductivity type;    a second transistor that has a source region and a drain region which are formed in the second-conductivity-type semiconductor region, the source and drain regions having the first conductivity type,    wherein at least one potential barrier having the second conductivity type is provided under the drain region of the first transistor and the source region and/or the drain region of the second transistor.    
   
   
       2 . The solid-state image sensing device according to  claim 1 , wherein the doping concentration of the at least one second-conductivity-type potential barrier is higher than the doping concentration of the second-conductivity-type semiconductor region.  
   
   
       3 . The solid-state image sensing device according to  claim 1 , wherein the at least one barriers are provided under the gate electrode of the first transistor and/or the gate electrode of the second transistor.  
   
   
       4 . The solid-state image sensing device according to  claim 1 , further comprising element isolation regions provided between the pixels, wherein the at least potential barrier is provided under the element isolation regions.  
   
   
       5 . A solid-state image sensing device having at least one pixel, the pixel comprising: 
 a photodiode that is constituted by a semiconductor region having a first conductivity type and a semiconductor region having a second conductivity type, the first conductivity type and the second conductivity type being opposite to each other; and    a transistor that has a source region and a drain region which are provided in the first-conductivity-type semiconductor region, the source and drain regions having the first conductivity type,    wherein a potential barrier having the second conductivity type is provided under the gate electrode of the transistor.    
   
   
       6 . The solid-state image sensing device according to  claim 5 , wherein at least one potential barrier having the second conductivity type is second-conductivity-type potential barrier is provided under the source region and/or the drain region of the transistor.  
   
   
       7 . The solid-state image sensing device according to  claim 5 , wherein the pixel further comprises a signal-charge storing region, which is provided in the first-conductivity-type semiconductor region to store signal charge generated by the photodiode, the signal-charge storing section having the first conductivity type and having a doping concentration higher than the first-conductivity-type semiconductor region.  
   
   
       8 . The solid-state image sensing device according to  claim 5 , wherein the doping concentration of the potential barrier is higher than the doping concentration of the second-conductivity-type semiconductor region.  
   
   
       9 . A solid-state image sensing device comprising: 
 a substrate having a first conductivity type;    a layer having a second conductivity type; and    a layer having the first conductivity type,    wherein the second-conductivity-type layer and the first-conductivity-type layer form a photodiode and at least one potential barrier is provided around a region where the photodiode is formed, the at least one potential barrier being provided by a region having the second conductivity type.    
   
   
       10 . The solid-state image sensing device according to  claim 9 , wherein the second-conductivity-type region is provided in the first-conductivity-type layer and the second-conductivity-layer is a buried layer.  
   
   
       11 . The solid-state image sensing device according to  claim 10 , wherein the second-conductivity-type region extends to the second-conductivity-type buried layer in the depth direction.  
   
   
       12 . The solid-state image sensing device according to  claim 10 , wherein the second-conductivity-type region comprises a plurality of second-conductivity-type regions that is arranged at a plurality of layers in the depth direction of the first-conductivity-type layer.  
   
   
       13 . The solid-state image sensing device according to  claim 12 , wherein the uppermost layer of the plurality of layers controls a charge transfer path from the photodiode to a transfer transistor.  
   
   
       14 . The solid-state image sensing device according to  claim 10 , wherein a portion adjacent to a semiconductor surface of the first-conductivity-type layer has a region having a doping concentration higher than the other regions.  
   
   
       15 . A camera system comprising the solid-state image sensing device according to  claim 9.