Active pixel sensor cell that minimizes leakage current

Claim 2

An active pixel sensor cell formed on a semiconductor substrate of a first conductivity type, the cell comprising: a plurality of spaced-apart active regions of a second conductivity type formed in the substrate, the active regions including a photodiode region and a row-select region, the photodiode and row-select regions each having a doping concentration; a first isolation region of the second conductivity type formed in the substrate to adjoin the photodiode region, the first isolation region having a doping concentration substantially less than the doping concentration of the photodiode region; a second isolation region of the first conductivity type formed in the substrate to adjoin the first isolation region, the second isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region; and a third isolation region of the second conductivity type formed in the substrate to adjoin the second isolation region and the row-select region, the third isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region.

Claim 3

The cell of claim 1 wherein the first isolation region and the second isolation region overlap.

Claim 4

The cell of claim 1 wherein the second isolation region and the third isolation region overlap.

Claim 5

The cell of claim 1 wherein the photodiode region and the row-select region are heavily doped.

Claim 6

The cell of claim 1 wherein the doping concentration of the first, second, and third isolation regions is approximately equal to a doping concentration of a low-density drain (LDD) region.

Claim 7

An active pixel sensor cell formed on a semiconductor substrate of a first conductivity type, the cell comprising: a plurality of spaced-apart active regions of a second conductivity type formed in the substrate, the active regions including a photodiode region and a row-select region, the photodiode and row-select regions each having a doping concentration; a first isolation region of the second conductivity type formed in the substrate to adjoin the photodiode region, the first isolation region having a doping concentration substantially less than the doping concentration of the photodiode region; a second isolation region of the first conductivity type formed in the substrate to adjoin the first isolation region, the second isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region; a third isolation region formed by an oxide layer on the surface of the substrate to adjoin the second isolation region; a fourth isolation region of the first conductivity type formed in the substrate to adjoin the third isolation region, the fourth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region; and a fifth isolation region of the second conductivity type formed in the substrate to adjoin the fourth isolation region and the row-select region, the fifth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region.

Claim 8

An active pixel sensor cell formed on a semiconductor substrate of a first conductivity type, the cell comprising: a plurality of spaced-apart active regions of a second conductivity type formed in the substrate, the active regions including a photodiode region and a row-select region, the photodiode and row-select regions each having a doping concentration; a first isolation region of the second conductivity type formed in the substrate to adjoin the photodiode region, the first isolation region having a doping concentration substantially less than the doping concentration of the photodiode region; a second isolation region of the first conductivity type formed in the substrate to adjoin the first isolation region, the second isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region; a third isolation region formed by an oxide layer on the surface of the substrate to adjoin the second isolation region; a fourth isolation region of the first conductivity type formed in the substrate to adjoin the third isolation region, the fourth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region; and a fifth isolation region of the second conductivity type formed in the substrate to adjoin the fourth isolation region and the row-select region, the fifth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region.

Claim 9

The cell of claim 6 wherein the first isolation region and the second isolation region overlap.

Claim 10

The cell of claim 6 wherein the fourth isolation region and the fifth isolation region overlap.

Claim 11

The cell of claim 6 wherein the photodiode and row-select regions are heavily doped.

Claim 12

The cell of claim 6 wherein the doping concentration of the first, second, fourth, and fifth isolation regions is approximately equal to a doping concentration of a low-density drain (LDD) region.