Hafnium dioxide, HfO2, thin films were prepared by radio frequency magnetron sputtering of thin hafnium layers, followed by an oxidation process. Ru was deposited on the HfO2 as the gate electrode. An equivalent oxide thickness of 12.5 was obtained in Ru/HfO2/n-Si metal oxide semiconductor (MOS) capacitor with a low leakage current density of 1.7 x 10(-2) A/cm(2) at Vg - V-FB = 1 V in accumulation. The work function of Ru gate extracted from capacitance-voltage analysis was 5.02 eV, suggesting Ru has the appropriate work function for p-MOSFETs. Using the conductance method, a high interface state density of 1.3 x 10(13) eV(-1) cm(-2) from the conduction band edge to the near midgap of Si was obtained in Ru/HfO2/n-Si MOS, compared to low interface density level of similar to 10(11) eV(-1) cm(-2) in p(+) poly Si/SiO2/n-Si MOS. To evaluate the thermal stability, the samples were subjected to a rapid thermal anneal in an argon ambient up to 900 S C. The electrical characteristics of Ru/HfO2/n-Si MOS capacitor are discussed in detail with post-metal annealing temperatures. (c) 2005 The Electrochemical Society.