Image sensor having 3-dimensional transfer transistor and its method of manufacture

Abstract

In an embodiment, an image sensor includes an isolation layer disposed in a semiconductor substrate to define a first active region and a second active region extending from the first active region. A photodiode is disposed in a portion of the first active region. A floating diffusion region is provided in the second active region at a position spaced apart from the photodiode. A transfer gate electrode is disposed on the second active region between the photodiode and the floating diffusion region. The transfer gate electrode is disposed to cover both sidewalls and an upper portion of the second active region. The transfer gate electrode has a region extending onto the first active region and overlapping the photodiode. The photodiode has a protrusion into the second active region at the portion adjacent to the transfer gate electrode. A deep n-impurity region of the photodiode extends in the protrusion.

1 . An image sensor, comprising:
 an isolation layer disposed in a semiconductor substrate and defining a first active region and a second active region extending from the first active region, the second active region having sidewalls defined by the isolation layer;   a photodiode having a shallow p-impurity region disposed in the first active region and a deep n-impurity region disposed below the shallow p-impurity region; a floating diffusion region in the second active region at a position spaced apart from the photodiode; and   an insulated transfer gate electrode disposed between the photodiode and the floating diffusion region to cover at least one of the sidewalls of the second active region so that a portion of the transfer gate electrode overlaps the first active region, wherein either one of the deep n-impurity region and the shallow p-impurity region has a protrusion into the second active region at a portion adjacent to the transfer gate electrode.   
   
   
       2 . The image sensor according to  claim 1 , wherein the protrusion is formed in a “U-shape”, a “V-shape” or a “W-shape” as seen in plan view. 
   
   
       3 . The image sensor according to  claim 1 , wherein the protrusion is the deep n-impurity region. 
   
   
       4 . The image sensor according to  claim 1 , wherein the protrusion is the deep n-impurity region and the shallow p-impurity region. 
   
   
       5 . The image sensor according to  claim 1 , wherein the insulated transfer gate electrode covers both sidewalls of the second active region. 
   
   
       6 . The image sensor according to  claim 1 , wherein the insulated transfer gate electrode covers both sidewalls and an upper portion of the second active region. 
   
   
       7 . The image sensor according to  claim 1 , wherein the floating diffusion region is a high concentration n-impurity region formed downward from the top of the second active region. 
   
   
       8 . An image sensor, comprising:
 an isolation layer disposed in a semiconductor substrate and defining a first active region and a second active region extending from the first active region, the second active region having sidewalls defined by the isolation layer;   a photodiode having a shallow p-impurity region disposed in the first active region and a deep n-impurity region disposed below the shallow p-impurity region; a floating diffusion region in the second active region spaced apart from the photodiode; and   an insulated transfer gate electrode disposed between the photodiode and the floating diffusion region to cover both of the sidewalls and an upper portion of the second active region so that a portion of the transfer gate electrode overlaps with the first active region, wherein the deep n-impurity region has a protrusion into the second active region at a portion adjacent to the transfer gate electrode.   
   
   
       9 . The image sensor according to  claim 8 , wherein the protrusion is formed in a “U-shape”, a “V-shape” or a “W-shape” as seen in plan view. 
   
   
       10 . The image sensor according to  claim 8 , wherein the floating diffusion region is a high concentration n-impurity region formed downward from the top of the second active region.