an image sensor having pixels that include two patterned semiconductor layers . the top patterned semiconductor layer contains the photoelectric elements of pixels having substantially 100 % fill - factor . the bottom patterned semiconductor layer contains transistors for detecting , resetting , amplifying and transmitting signals charges received from the photoelectric elements . the top and bottom patterned semiconductor layers may be separated from each other by an interlayer insulating layer that may include metal interconnections for conducting signals between devices formed in the patterned semiconductor layers and from external devices .