Provided are a high-quality CMOS image sensor and a photo diode, which can be fabricated in sub-90 nm regime using nanoscale CMOS technology. The photo diode includes: a p-type well; an internal n-type region formed under a surface of the p-type well; and a surface p-type region including a highly doped p-type SiGeC epitaxial layer or a polysilicon layer deposited on a top surface of the p-type well over the internal n-type region. The image sensor includes: a photo diode including an internal n-type region and a surface p-type region; a transfer transistor for transmitting photo-charges generated in the photo diode to a floating diffusion node; and a driving transistor for amplifying a variation in an electric potential of the floating diffusion node due to the photo-charges. The image sensor further includes a floating metal layer for functioning as the floating diffusion node and applying an electric potential from a drain of the transfer transistor to a gate of the driving transistor.