The electric-mirror sputtering system involves the use of a planar and a cylindrical target in a special configuration that is useful for depositing high-quality films at low gas pressure (below 0.1 Pa). This article describes how a radio-frequency-mode (rf-mode) operation is combined with high-density plasma generation in electric-mirror sputtering for film deposition. To generate a high-density plasma by confining high-energy secondary electrons emitted from the targets between them, rf voltages must be applied to both targets with a phase difference of no more than 30 degrees. Thin films are deposited at high rates, an order of magnitude higher than in a system with only a cylindrical target, in a low gas pressure atmosphere below 0.1 Pa, without extremely high-energy ion bombardment during deposition. Uniform films can be obtained over almost the same area as the internal area of the cylindrical target by optimizing the substrate location.