Cu(In,Ga)Se-2 (CIGSe) thin films were prepared by radio frequency (RF) magnetron sputtering at room temperature, following vacuum annealing at different temperatures. We have investigated the effect of annealing temperature (150-550 degrees C) on the phase transformation process of the CIGSe films. The as-deposited precursor films show a near stoichiometry composition and amorphous structure. Composition loss of the films mainly occur in the annealing temperature range of 150-300 degrees C. Comparing with samples annealed at 300 degrees C, films annealed at 350 degrees C or higher temperatures exhibit almost similar composition and polycrystalline chalcopyrite structure. Crystal quality of the films improves with increasing annealing temperature. Reflectance spectra of the annealed films show interference fringe pattern. The calculated refractive indexes of the films are in the range of 2.4-2.5. (C) 2012 Elsevier B. V. All rights reserved.