Fomnation of giant-grain copper thin films on SiO 2 by a low-kinetic energy particle process followed by thermal annealing has been investigated. When Cu films are grown on SiO 2 by the process under a sufficient amount of energy deposition, they exhibit almost perfect crystal orientation conversion from Cu(111) to Cu(100) upon themnal annealing. Such crystal orientation conversion is accompanied by the giant grain growth in the film as large as 100 μm. With regard to these phenomena, the effects of the ion flux density and of the ion bombardment energy have been studied