A method of manufacturing an image sensor having a backside illumination (BSI) structure includes forming a wiring unit on a front side of a semiconductor substrate, forming an anti-reflective layer in an active pixel sensor (APS) region on a back side of the semiconductor substrate, a photodiode being between the back and front sides of the semiconductor substrate, forming an etch stopping layer on the anti-reflective layer, forming an interlayer insulating layer on the etch stopping layer, the interlayer insulating layer having an etch selectivity with respect to the etch stopping layer, and etching the interlayer insulating layer in the APS region using the etch stopping layer as an etch stopping point.