Thin films of Er-doped Ta2O5 have been synthesized by RF sputtering. The influence of annealing temperature, number of Er tablets and annealing time on the structural properties of grown films, has been studied. The samples annealed bellow 800°C show amorphous nature. However, the sample annealed at 800°C and above shows crystalline nature of the film with β–Ta2O5 (orthorhombic) and δ–Ta2O5 (hexagonal) phase. The crystalline structure of the film is disturbed with the increase in Er concentration.