Method for forming an image sensing device

A method for forming an image sensing device, comprising:

• providing a substrate having a first conductivity type;
• forming an epitaxy layer having the first conductivity type on the substrate, wherein the epitaxy layer comprises a first pixel area corresponding to a first incident light, a second pixel area corresponding to a second incident light, and a third pixel area corresponding to a third incident light, and wavelength of the first incident light is longer than that of the second incident light and wavelength of the second incident light is longer than that of the third incident light;
• forming a first deep well in a lower portion of the epitaxy layer for reducing pixel-to-pixel talk of the image sensing device by implantation using a mask, wherein the mask has a cover corresponding to the first pixel area and a portion of the mask corresponding to the second pixel area and the third pixel area are exposed, such that the implanting process can form the first deep well at least in the second pixel area and the third pixel area of the epitaxy layer, and at least a portion of the first pixel area does not comprise the first deep well;
• and
• forming a second deep well in a lower portion of the epitaxy layer, wherein the second deep well is at least disposed in the first, second and third pixel area, and the portion of the first pixel area not comprising the first deep well comprises the second deep well;
• and
• forming a photodiode in an upper portion of the epitaxy layer.