The impact of primary ion bombardment conditions on SIMS depth profiles through HfO2 high-k films was investigated. Independent of the sputter beam conditions, Hf depth profiles show the apparent presence of Hf throughout the film, as well as tailing of the Hf signal into the substrate. A long tail region of decay length similar to10 nm seen for reactive and inert sputter beams, largely independent of the energy, is inconsistent with simple ion beam-induced mixing. Chemical state depth profiles by XPS show that Hf transforms into metallic Hf-0 in the Si substrate, corresponding to the tail regions of SIMS profiles. SIMS and XPS backside profiles confirm that Hf is not initially present in the Si substrate. Hf chemical state changes observed in XPS sputter depth profiles depend on the film stoichiometry, as seen with HfSxOy films of different composition. (C) 2004 Elsevier B.V. All rights reserved.