Provided is an image sensor. The image sensor includes a semiconductor substrate, an interlayer dielectric, metal interconnections, a first electrode, a lower electrode, a second electrode, and a photodiode. The semiconductor substrate has at least one transistor thereon. The interlayer dielectric is on the semiconductor substrate. The metal interconnections pass through the interlayer dielectric. The first electrode is in the interlayer dielectric between the metal interconnections. The lower electrode is on the interlayer dielectric to connect to the metal interconnection. The second electrode is on the interlayer dielectric at a position corresponding to the first electrode, and a gap region is between the second electrode and the lower electrode. The photodiode is on the interlayer dielectric with the lower electrode and the second electrode.