Cu/Te multi-layers with a composition of 50 at% of Te were deposited onto glass substrates by radio frequency (RF) sputtering. Their structure was investigated by the grazing-incidence X-ray diffraction technique (GIXD). The spectra of the as-deposited sample show the formation of hexagonal Cu 2− x Te and the presence of free Te. The heat treatments at 450 K during 30 min, 1 h and 2 h show the progressive disappearance of the Cu 2− x Te phase and the appearance of a new compound—the orthorhombic rickardite Cu 7 Te 5 , suggesting that a Cu 2− x Te→Cu 7 Te 5 transformation took place. The samples annealed for a period of 3 h at 450 K show that Cu 7 Te 5 completely disappeared in favour of Cu 2− x Te and, more precisely, the Cu 0.647 Te 0.353 phase dominates the spectra, suggesting that a Cu 7 Te 5 →Cu 2− x Te inverse phase transformation took place. The results are discussed in light of the strong inter-diffusion that occurred between the Cu and Te layers during the deposition at ambient temperature and to elemental diffusion during annealing. The phase transformations are attributed to a diffusion-induced homogenization of the sample and a loss of Te by sublimation during annealing for an extended time.