The interface state densities of wet anodic oxide layers on Si are normally very high and, therefore, there is need for special post-treatments. Repetitive oxidation/hydrogenation cycles in the current oscillating regime lead to improved passivation of the SiO2/Si interface. The atomic force microscopy (AFM) images reveal the formation of macroscopically rough surfaces (holes with a diameter of at least 100 nm and a depth of up to 10 nm). This kind of surface structure is more favourable to decrease the strain induced by the Si-O-Si bond angle mismatch. This peculiarity of Si surfaces conditioning in acidic NH4F solutions leads to a reduction of the defect concentration at the SiO2/Si interface without further processing.