We present in this paper the results of advanced characterization, by photoemission using the soft x‐rays of a synchrotron source, of the interface between chemically oxidized Si and 0.6 nm HfO2. The benefits of such a source enables us to determine the chemical nature and estimate the spatial structure of the intermediate layer between the high‐&kgr; material and the Si substrate. It is shown that this layer consists of two sub‐layers, the first being pure SiO2extending over 0.64 nm and the second being Hf‐silicate (HfO2)x(SiO2)1−xwith x=0.44 and a thickness estimated to be 0.22 nm. The present approach should apply to the study of other Si/high‐&kgr; materials interfaces. © 2003 American Institute of Physics