Very low-temperature formation of high-quality thin films having ideal interface characteristics has been demonstrated by a high-precision controlled low-energy ion bombardment process. In this process, films are grown under concurrent bombardment of the growing film surface by low-energy ions, thus activating the surface in situ to allow low-temperature crystal growth. The process has been realized by two types of plasma processing equipment : the r.f.-d.c. coupled mode plasma processing system and the dual frequency plasma processing system. In these systems, the most important process parameters, such as ion bombardment energy, ion flux density and film growth rate, are all independently and precisely controlled. The low-energy ion bombardment process has been successfully applied to the growth of in situ doped device-grade epitaxial silicon films at a temperature as low as 250-degrees-C. Formation of giant grain copper thin films has been also shown by the process. The giant grain copper thin films exhibit excellent properties as a ULSI interconnect material characterized by low thin film resistivity equivalent to the bulk value and large electromigration resistance. The basic features of the dual frequency system and its application to new process technologies are also discussed.