In an example embodiment, an image sensor includes a semiconductor layer and isolation regions disposed in the semiconductor layer. The isolation regions define active regions of the semiconductor layer. The image sensor further includes photoelectric converters disposed in the semiconductor layer and at least one wiring layer disposed over a top surface of the semiconductor layer. The image sensor also includes color filters disposed below a bottom surface of the semiconductor layer and lenses disposed below the color filters. Each lens is arranged to concentrate incoming light into an area spanned by a corresponding photoelectric converter.