1. A CMOS image sensor comprising: a first gate electrode on a semiconductor substrate; a photodiode in the semiconductor substrate on one side of the first gate electrode; a floating diffusion area in the semiconductor substrate on an opposite side of the first gate electrode; a capacitor comprising a lower capacitor electrode connected to the floating diffusion area, a dielectric layer on the lower capacitor electrode, and an upper capacitor electrode; and a drive transistor having a second gate electrode connected to the floating diffusion area and the lower capacitor electrode.