Image sensor including dual isolation and method of making the same

An image sensor comprising:

• a substrate having a pixel region and a periphery region;
• a photodiode in the pixel region;
• a plurality of first isolation structures in the pixel region, wherein the photodiode is between adjacent first isolation structures of the plurality of first isolation structures, and at least one of the plurality of first isolation structures comprises a first trench having a first depth;
• and
• a plurality of second isolation structures in the periphery region, wherein at least one of the plurality of second isolation structures comprises a second trench having a second depth greater than the first depth,
• wherein the pixel region includes only MOS devices having a first dopant type and the periphery region includes MOS devices having the first dopant type and a second dopant type, and the second dopant type is opposite the first dopant type.

An image sensor comprising:

• a silicon substrate having a pixel region and a periphery region;
• a photodiode in the pixel region;
• logic circuitry in the periphery region;
• a first shallow trench isolation (STI) structure in the pixel region adjacent to the photodiode, wherein the first STI structure extends from a surface of the silicon substrate to a depth ranging from 1100 angstroms to 1300 angstroms;
• and
• a second STI structure in the periphery region, wherein the second STI structure extends from the surface of the silicon substrate to a depth ranging from 3100 angstroms to 3300 angstroms;
• wherein the pixel region includes only NMOS devices and the periphery region includes NMOS devices and PMOS devices.