An image sensor includes first pixels, second pixels and a deep trench. The first pixels are formed in an active region of a semiconductor substrate, and configured to measure photo-charges corresponding to incident light. The second pixels are formed in an optical-black region of the semiconductor substrate, and are configured to measure black levels. The deep trench is formed vertically in a boundary region of the optical-black region, where the boundary region is adjacent to the active region, and configured to block leakage light and diffusion carriers from the active region.