A complete picture of breakdown is presented and compared with a full set of experiments. First, an analytical model for the breakdown statistics is considered as far as its properties for the thickness scaling of breakdown. Second, a hydrogen-based quantitative picture for the defect generation process is presented. A two-step mechanism consisting in the release of protons from suboxide bonds at the anode interface and the subsequent reaction with oxygen vacancies is considered. A new kinetic approach is presented to consider the combination of interface and bulk reactions in the two-step model of breakdown. The model is successfully compared with a complete set of breakdown measurements. The voltage and thickness dependencies of breakdown are nicely captured by the model with a physically reasonable set of parameters. An heuristic model for the temperature dependence is also considered. (C) 2002 Elsevier Science Ltd. All rights reserved.