A method for manufacturing a CMOS image sensor is provided. The method can include forming an interlayer dielectric layer on a semiconductor substrate including a gate electrode, photodiode area, and LDD region; selectively removing the interlayer dielectric layer such that the interlayer dielectric layer remains on the photodiode area; performing a first heat treatment process; sequentially forming a first insulating layer and a second insulating layer on the semiconductor substrate, where the etching selectivity of the first insulating layer is different from the etching selectivity of the second insulating layer; selectively etching the second insulating layer to form spacers on sidewalls of the gate electrode; selectively removing the first insulating layer to expose a source/drain area and forming a high-density N-type diffusion area in the exposed source/drain area; performing a second heat treatment process; and forming a metal silicide layer the high-density N-type diffusion area.