SrHfON thin films were prepared on p-type Si substrates by reactive radio-frequency sputtering deposition. The effects of annealing on the interface between SrHfON film and Si substrate, the structure and the electrical properties of the as-deposited and annealed ?lms have been investigated systematically. The results of XRD and HRTEM show that the SrHfON films are amorphous even after annealing at 900 °C. The interface between SrHfON film and Si substrate is composed of HfSixOy and SiO2 confirmed by XPS. The measurements indicate that MOS capacitors using the SrHfON films as gate dielectrics have lower leakage current densities and the leakage current densities decrease with increasing of RTA temperatures. The leakage current densities at Vg=+1 V for the as-deposited and annealed ?lms are 4.3×10-6 A/cm2 and 1.2×10-7 A/cm2, respectively. The analyses results show that SrHfON films will be a promising candidate for replacing SiO2 gate dielectric.