An image sensor and a manufacturing method thereof are provided. The image sensor can comprise: a semiconductor substrate, a first dielectric, a second dielectric pattern, a planarization layer, and a color filter. The semiconductor substrate comprises a photodiode. The first dielectric is disposed on the semiconductor substrate. The second dielectric pattern is disposed on the first dielectric and comprises a trench in a region corresponding to the photodiode. The planarization layer is disposed in the trench. The color filter is disposed on the planarization layer disposed on the photodiode.