We adopt first-principle approach to calculate potential energy surfaces for alpha-quartz and -cristobalite silicon dioxide (SiO2) with hydrogenated impurities in the neutral, positive, and negative charged states. It is expected that H atoms in SiO2 have an important role to generate leakage current paths. In this paper, we calculate stable and unstable positions of a migrating H atom and discuss electrons or holes trapping mechanism. These results clarify that the dynamics of the H atom in the neutral, negative, and positive charged states should be different from one another, and therefore, the mechanism of the dielectric break down of SiO2 also depends on the charged environment. Based on the regional density functional theory, we have calculated the effective charge tensor density of the migrating H atom in the neutral state. (C) 2003 Elsevier Science B.V. All rights reserved.