Image sensor and method for fabricating the same

Abstract

An image sensor includes a substrate, a photoelectric conversion region in the substrate with the substrate defining a substrate trench on the photoelectric conversion region, a floating diffusion region adjacent to a side surface of the substrate trench, in the substrate, a gate dielectric film that extends along the side surface and a lower surface of the substrate trench and a transfer gate electrode which includes a lower gate that fills a portion of the substrate trench on the gate dielectric film and has a first width, and an upper gate that has a second width smaller than the first width on the lower gate. The gate dielectric film includes a lower dielectric film interposed between the substrate and the lower gate and has a first thickness, and an upper dielectric film adjacent to the floating diffusion region and has a second thickness greater than the first thickness.