An image sensor semiconductor device includes a semiconductor substrate and a first photodiode disposed in the semiconductor substrate and configured to generate charges in response to radiation. The image sensor semiconductor device also includes a first transistor disposed adjacent to the first photodiode, and a second transistor disposed over the first photodiode, wherein the first transistor and the second transistor are configured to generate at least one electric field to move the charges generated by the first photodiode. The image sensor device further includes a floating diffusion region configured to store the moved charges.