Patent ID: 7514733
Filing Date: 2009-04-07
Classification: H01L

Abstract:
1. A CMOS image sensor, comprising: a semiconductor substrate having a photodiode therein that extends adjacent a surface thereof, said photodiode comprising a semiconductor anode region of first conductivity type and a semiconductor cathode region of second conductivity type therein; a floating diffusion region of second conductivity type in said semiconductor substrate; a MOS transfer transistor having a gate electrode on a first portion of the surface and a first conductivity type channel region extending to the first portion of the surface, said MOS transfer transistor configured so that said floating diffusion region represents a source of said MOS transfer transistor and the channel region extends between said photodiode and said floating diffusion region; a first impurity region of first conductivity type extending in a drain-side portion of the channel region, said first impurity region sufficiently doped so that a drain-side of the channel region adjacent said photodiode is more highly doped with first conductivity type dopants relative to a source-side of the channel region extending adjacent the source of said MOS transfer transistor; and a second impurity region of second conductivity type extending underneath and forming a P-N rectifying junction with said first impurity region; wherein said first impurity region forms a non-rectifying junction with the semiconductor anode region of first conductivity type and a P-N rectifying junction with the semiconductor cathode region of second conductivity type; and wherein the second impurity region extends entirely underneath the gate electrode and forms a non-rectifying junction with the semiconductor cathode region.