Patent ID: 8629023

Claim:
A method of making a complementary metal-oxide semiconductor (CMOS) image sensor, the method comprising: doping regions in a substrate to form MOSFET transistors in first and second areas of the substrate, wherein the MOSFET transistors in the first area are used to form pixel sensors of a pixel array, and wherein the MOSFET transistors in the second area are used to form a logic circuit; forming a field oxide in a region around the first area to isolate the MOSFET transistors in the first area from the MOSFET transistors in the second area; depositing a first insulating layer concurrently over both the first and second areas of the substrate; removing the first insulating layer from the second area while leaving the first insulating layer over the first area intact; depositing a second insulating layer concurrently over both the first and second areas of the substrate; removing the second insulating layer from selected regions of the second area to form gates of the MOSFET transistors in the logic circuit; and removing both the first and second gate insulating layers from selected areas of the first area to form gates of the MOSFET transistors of the pixel sensors, wherein the gate of each MOSFET transistor in the first area has a thickness corresponding to a combined thickness of the first and second insulating layers, and wherein the gate of each MOSFET transistor in the second area has a thickness that is less than a combined thickness of the first and second insulating layers.