An image sensor includes a substrate having a first pixel region and a second pixel region adjacent to the first pixel region, a device isolation layer between the first pixel region and the second pixel region and isolating the first pixel region and the second pixel region from each other, a first transistor disposed in the first pixel region, a second transistor disposed in the second pixel region, and a wiring structure electrically connecting the first transistor and the second transistor. The device isolation layer has a deep trench isolation (DTI) structure which extends from a top surface toward a bottom surface of the substrate.