An image sensor includes a first device isolation layer separating a plurality of pixels from one another, and a second device isolation layer disposed along inner side surfaces of parts of the first device isolation layer that extend around the pixels. The second device isolation layer delimits an active region of the semiconductor substrate. Each pixel includes a photoelectric converter, a floating diffusion region, a ground region, and a gate of a transfer transistor. The gate extends into the active region of the semiconductor substrate. The ground region is electrically connected to a ground voltage terminal.