An image sensor includes a lower metal interconnection, an interlayer dielectric, a first substrate, a photodiode, an upper electrode and an amorphous silicon layer. The lower metal interconnection and the interlayer dielectric are formed over the first substrate including a pixel region and a peripheral region. The photodiode is formed over the pixel region of the first substrate. The upper electrode layer is connected to the photodiode. The amorphous silicon layer is formed between the photodiode and the interlayer dielectric.