A new method for characterizing dielectric properties of high‐k films was investigated with an open‐circuit potential (OCP) measurement during etching of a film in a solution. The linear dependence of OCP on etching time was clearly observed. The areal density of the adsorbed ion charges on the film surface was estimated from the slope in the time dependence of OCP, and it was shown to be closely related to the electronegativity difference between the atoms on the film surface and etchant atoms in the solution. This finding implies that the time‐dependent OCP measurement is useful for evaluating the ionic characteristic of dielectric materials. The application of this technique to a depth‐profiling analysis of a multilayer dielectric film was also investigated. The transition of the etching surface from one layer to another one was clearly observed, which suggests that the depth‐dependent dielectric properties of high‐k films can be characterized with this method. © 2003 American Institute of Physics