Nitrogen is incorporated with different contents into ultra-thin HfTiO dielectric films deposited on Si (100) substrate by radio frequency (RF) magnetron sputtering under a N-2 atmosphere. The improved thermal stability and surface microstructure are demonstrated by X-ray diffraction (XRD) and atomic force microscope (AFM) due to the incorporation of nitrogen. The optical characterization of the ultrathin HfTiON films exhibits a large band gap attributed to nitrogen doping, and a reduction in band gap with increase of N-doped concentration. More importantly, electrical properties of ultra-thin HfTiON films related to different nitrogen-incorporated content are systematically investigated. The N-doped content of HfTiON films deposited under Ar/N-2 flow ratio of 30/15 (sccm) has been proved to be an optimal amount, based on which HfTiON films through 500 degrees C rapid thermal annealing (RTA) treatment further achieve the most favorably excellent electrical properties in terms of a lower gate leakage current density of 7.72 x 10(-6) A/cm(2) and a higher permittivity of 35.31. Moreover, the dominant conduction mechanisms of Pt/HfTiON/p-Si structures for both as-deposited and annealed HfTiON films are discussed by data fitting method in details. (C) 2013 Elsevier B. V. All rights reserved.