A method for fabricating a CMOS image sensor forms silicon nitride (SiN) layer on a pad. Microlenses, having a minimum height and footprint according to a desired packing density of the lenses, are fabricated of an oxide film and a nitride film deposited on the silicon nitride. Since the lenses have a low height, a refractive index of the lenses may be improved. A sidewall spacer type inner lens may be additionally formed below a main lens curvature to aid in overcoming problems caused by a single-lens structure.