The present disclosure provides for multiple gate dielectric semiconductor structures and methods of forming such structures. In one embodiment, a method of forming a semiconductor structure includes providing a substrate including a pixel array region, an input/output (I/O) region, and a core region. The method further includes forming a first gate dielectric layer over the pixel array region, forming a second gate dielectric layer over the I/O region, and forming a third gate dielectric layer over the core region, wherein the first gate dielectric layer, the second gate dielectric layer, and the third gate dielectric layer are each formed to be comprised of a different material and to have a different thickness.