A capacitor including a substrate, a conductive layer, a middle dielectric material layer, a first dielectric material layer, and a second dielectric material layer is provided. The conductive layer includes a first electrode and a second electrode, and the conductive layer is located over the substrate. The middle dielectric material layer is located between the first electrode and the second electrode. The first dielectric material layer is located between the middle dielectric material layer and the first electrode. The second dielectric material layer is located between the middle dielectric material layer and the second electrode. The dielectric constant of the middle dielectric material layer is different from the dielectric constants of the first dielectric material layer and the second dielectric material layer.