Patent ID: 8363141

Claim:
A solid-state image pickup device comprising: a first semiconductor region; an element isolation region; and a plurality of unit cells, each including: a photoelectric conversion element; a transfer gate electrode configured to transfer charge generated in the photoelectric conversion element; a floating diffusion configured to store the transferred charge; and an amplifying transistor having a gate electrode connected to the floating diffusion, wherein the element isolation region and the plurality of unit cells are disposed above the first semiconductor region, wherein the photoelectric conversion element includes a second semiconductor region of a first conductivity type, a third semiconductor region of a second conductivity type configured to store the charge, and a fourth semiconductor region of the second conductivity type having an impurity concentration lower than the third semiconductor region; and the semiconductor regions are arranged in an order the third, fourth, and second semiconductor regions from a light receiving surface, and wherein the second semiconductor region includes a portion constituting the photoelectric conversion element and a portion disposed under the element isolation region and the floating diffusion, wherein the first semiconductor region is disposed under the second semiconductor region and has an interface with the second semiconductor region, and wherein the interface between the first semiconductor region and the portion of the second semiconductor region constituting the photoelectric conversion element is located at a first depth, whereas the interface between the first semiconductor region and the portion of the second semiconductor region under the element isolation region and the floating diffusion is located at a second depth smaller than the first depth.