An image sensing device includes a photoelectric conversion element, a floating diffusion (FD) region, and a transfer gate. The photoelectric conversion element is disposed in a substrate, and generates photocharges in response to incident light. The floating diffusion (FD) region is disposed over the photoelectric conversion element, and stores the photocharges generated by the photoelectric conversion element. The transfer gate transfer the photocharges generated by the photoelectric conversion element to the floating diffusion (FD) region in response to a transmission signal. The transfer gate includes a horizontal gate disposed over the photoelectric conversion element, and a vertical gate coupled to the horizontal gate. The vertical gate is positioned at a side of the photoelectric conversion element, and surrounds the photoelectric conversion element.