Patent ID: 6169318
Filing Date: 2001-01-02
Classification: H01L

Abstract:
A CMOS image sensor element formed in a semiconductor substrate of a first doping type for converting impinging electromagnetic radiation into electric signals, the sensor element comprising: a first well formed in said substrate and doped with the first doping type to a higher doping level than the substrate, wherein at last a portion of said first well defines the gate region of a first transistor; a second well formed in said first well and doped with a second doping type, said second well defining the source of the first transistor; a third well formed substantially in said substrate and doped with the second doping type, said third well defining a photodiode and the drain of the first transistor; and a fourth well formed in said substrate and doped with the first doping type to a higher doping level than the substrate, said fourth well defining the gate region of a second transistor; so that electric charges generated by the electromagnetic radiation in the semiconductor substrate proximate to said third well and said fourth well are preferably collected in said third well whereby quantum efficiency can be maintained with reduced feature size of said sensor element.