Provided is a method of fabricating a complementary metal oxide silicon image sensor. The method includes: applying a passivation oxide and a passivation nitride after forming a pad; selectively removing the passivation nitride in a pad region and a pixel region by a photolithography process, and performing a first cleaning process; performing a hydrogen anneal process; opening the pad by removing the passivation oxide in the pad region and performing a second cleaning process; applying a pad protective layer; performing a color filter array process, a planarization process, and a microlens process after the applying of the pad protective layer; and removing the pad protective layer in the pad region.