We fabricated nanocrystalline Ge films using radio-frequency (RF) magnetron plasma sputtering deposition under a high Ar-gas pressure. The Ge nanograins changed from amorphous to crystalline when the distance between the Ge sputtering target and the substrate was decreased to 5 mm and the RF input power was 11.8 W/cm 2 (60 W), where the deposition rate was as high as 660 nm/min. In addition, the size of the nanocrystalline grains increased from 100 to 307 nm when the RF input power for plasma production was increased from 11.8 W/cm 2 (60 W) to 17.7 W/cm 2 (90 W). In the developed narrow-gap plasma process at sub-Torr pressures, nanocrystalline Ge films were successfully fabricated on Cu substrates at low temperatures, without the substrate being heated. However, when annealing was conducted under an N2 atmosphere, which is the conventional method to induce solid-phase crystallization, the amorphous Ge layer on a Cu substrate changed to a Cu3Ge crystal layer through interdiffusion of Ge and Cu atoms at 400-500 °C.