Dielectric degradation of an intentionally Cu-contaminated SiO2 film on a Si substrate was investigated using conducting atomic force microscopy and metal-oxide-semiconductor capacitors. Comparison of the results of both measurements clarified that local oxide leakage currents increased at random points except at the Cu particles. At the Cu particles, accelerated thermal oxidation leads to the formation of a thick SiO2 layer at the interface with the Si substrate and suppression of the oxide leakage current. A combination of electrical evaluations and total reflection X-ray fluorescence analyses indicated that a high Cu concentration on a SiO2 surface induced low-voltage dielectric breakdown, and a low Cu concentration inside the SiO2 film induced high leakage current in a low electric field range. (C) 2004 The Electrochemical Society.