Abstract: A CMOS image sensor, a first dielectric layer is formed on a first surface of a semiconductor substrate, and a plurality of lower microlenses having a bottom surface in the shape of an arc concave structure and located directly above the corresponding photodiode are formed in the first dielectric layer. A plurality of upper microlenses having a top surface in the shape of an arc convex structure and located directly above the corresponding lower microlens are formed on the top surface of the first dielectric layer. The refractive index of the material of the upper microlens is greater than or equal to the refractive index of the material of the lower microlens, and the refractive index of the material of the lower microlens is greater than the refractive index of the first dielectric layer.