Oxygen plasma treatment process was used to passivate the non-stoichiometric HfO2 films deposited by magnetron sputtering. After optimal oxygen plasma treatment, the gate leakage of HfO2 films would be reduced and dielectric breakdown voltage would be improved to 30 percentage. XPS spectrum was used to analysis the non-stoichiometric HfO2 films after oxygen plasma treatment which demonstrate a higher concentration of incorporated oxygen atoms at the surface in comparison to the bulk HfO2. This simple method can maintain high-k dielectric deposition process at room temperature by sputtering. It would be useful for fabrication thin film transistor on polymer based substrate in the future. (C) 2011 Published by Elsevier B.V.