A stripline resonator has a center conductor between layers of dielectric which are, in turn, between ground planes. The center conductor is made of a high-temperature superconducting material, preferably having a total superconductor thickness from at least about one micron to at least about one-hundred microns. The superconducting material has an electromagnetic penetration depth and the ratio of the thickness of the superconductor to the penetration depth is from at least about 4:1 to at least about 100:1. The center conductor may be formed of a substrate coated with the high-temperature superconducting material so that the center conductor is discrete from the dielectric element. The center conductor may have a length which is greater than the length of the dielectric element.