Bi5Nb3O15 (B5N3) thin films were well formed on a Pt/Ti/SiO2/Si substrate using radio-frequency magnetron sputtering. The crystalline B5N3 phase was developed for the films grown at temperatures above 450 degrees C, but it decomposed into the BiNbO3 phase when the growth temperature exceeded 550 degrees C, probably due to the evaporation of Bi2O3. The dielectric constant (k) of the B5N3 film grown at room temperature was approximately 42 and increased with increasing growth temperature, reaching a maximum value of 160 for the film grown at 550 degrees C. In particular, the B5N3 films grown in the temperature range of 200-300 degrees C showed a high k value of 70 with a low dissipation factor (< 1.0%), and their leakage current density was very low with a high breakdown voltage. Therefore, B5N3 films grown at low temperatures (<= 300 degrees C) can be a good candidate material for metal-insulator-metal (MIM) capacitors which require low processing temperatures. (C) 2008 The Electrochemical Society.