A method of fabricating a CMOS image sensor includes forming a substrate structure that includes a first substrate, a second substrate, and an index matching layer containing nitrogen and an oxide layer between the first and second substrates, and, forming at least one light-sensing device in the second substrate, and after forming the substrate structure, forming a metal interconnection structure on a first surface of the second substrate, the first surface facing away from the first substrate, such that the at least one light sensing device is between the metal interconnection structure and the index matching layer and the oxide layer, the metal interconnection structure being electrically connected to the at least one light-sensing device.