An image sensor includes: photodiodes arranged in a substrate; active pillars connected to the photodiodes and extending in a vertical direction perpendicular to a bottom surface of the substrate; at least two transistors stacked in the vertical direction, wherein portions of the active pillars are channel areas of the at least two transistors; a floating diffusion (FD) area disposed under a transfer transistor, which is one of the at least two transistors, wherein the FD area is configured to receive charge from the photodiode through the transfer transistor and the portions of the active pillars; and a light transmitting layer disposed on a top surface of the substrate.