Sol–gel-derived SrTa 2 O 6 thin films were fabricated at a low temperature of 500 °C. To improve their leakage current properties, additional UV/O 3 -assisted annealing was performed from room temperature to 290 °C. UV/O 3 treatment at 290 °C gave a very low leakage current that was six orders of magnitude lower than that of an untreated thin film. During UV/O 3 -assisted annealing, Si and Ti ions diffused from the substrates into the SrTa 2 O 6 thin films and occupied the Ta 5+ sites, subsequently generating Si − and Ti − . At a heating temperature of 290 °C, large amounts of Ti ions diffused throughout the SrTa 2 O 6 thin film. These Ti ions contributed to the generation of inactive combinations of and , which greatly reduced oxygen vacancies (V o ). Thus, the leakage current was significantly reduced.