Provided are a photomask, an image sensor, and a method of manufacturing the image sensor. The image sensor can include photodiode structures, color filters, a planarization layer, and microlenses. The photodiode structures can be disposed on a semiconductor substrate according to unit pixel. The color filters can be disposed on the semiconductor substrate in a matrix arrangement above the photodiode structures. The planarization layer can cover the entire semiconductor substrate and includes cavities in regions of the planarization layer corresponding to boundaries between the color filters. The cavities may be arranged at boundaries between unit pixels. The microlenses can be disposed on the planarization layer such that portions of the microlenses are arranged in the cavities of the planarization layer.