A complementary metal-oxide-semiconductor (CMOS) image sensor is provided. The CMOS image sensor may include an epitaxial layer having a first conductivity type and having first and second surfaces, a first device isolation layer extending from the first surface to the second surface to define first and second pixel regions, a well impurity layer of a second conductivity type formed adjacent to the first surface and formed in the epitaxial layer of each of the first and second pixel regions, and a second device isolation layer formed in the well impurity layer in each of the first and second pixel regions to define first and second active portions spaced apart from each other in each of the first and second pixel regions.