Embodiments relate to a complementary metal oxide semiconductor (CMOS) image sensor. According to embodiments, the CMOS image sensor may include a semiconductor substrate, an interlayer insulating layer, a color filter layer, an overcoat layer, and a plurality of microlenses. The semiconductor substrate may include a plurality of photodiodes and transistors with a constant interval. The color filter layer may be formed on the interlayer insulating layer, and respective color filters of the color filter layer correspond to respective photodiodes. The overcoat layer may have rounded trenches at a portion corresponding to each photodiode and may be formed on a surface of the semiconductor substrate. Each of the plurality of microlenses may have a convex lens shape and is formed inside the trench.