The HfO2/Si interface stability has been investigated by using a rapid thermal annealing (RTA), an inductively coupled plasma (ICP) and a reactive sputtering, as a comparison of thermal and plasma oxidations of the Hf/Si interface. Reduction in both capacitance equivalent thickness (CET) and leakage current density (J(g)) was difficult to be attained by the thermal oxidation since it accompanies the crystalline HfO2 with SiO2-Iike interface. Advantage is found for the plasma oxidation technique to oxidize Hf metal at low temperatures remaining the HfO2 in an amorphous phase with silicate interface. Reduction in both CET and J(g) was attained by the plasma oxidation and a Hf metal pre-deposition technique. (C) 2003 Elsevier Science B.V. All rights reserved.