"Finally, a part of the tunable film should be etched away to expose the bottom electrode. [0061] The substrate layer in the described varactors may be comprised of MgO, alumina (AL2O3), LaAlO3, sapphire, quartz, silicon, gallium arsenide, and other materials that are compatible with the various tunable films and the electrodes, as well as the processing used to produce the tunable films and the el" . . . . . . . .