1. A method of forming an image sensor having a pixel array, the method comprising the steps of: forming periphery elements of the image sensor over a substrate; forming an oxide layer over the periphery elements; forming an opening in the oxide layer in a pixel array area; forming an epitaxial layer in the opening; forming at least one well within the epitaxial layer; forming photosensitive elements of the pixel array within the at least one well in the epitaxial layer including at least one photodiode, wherein the at least one well extends through a thickness of the epitaxial layer into the substrate; and forming at least one of a transfer gate, a reset transistor, a select transistor, and a source follower output transistor within the epitaxial layer.