The influence of medium dose ion implantation on the dielectric breakdown reliability of thin gate oxide is discussed. Medium dose ion implantation and subsequent high temperature oxidation degrade the dielectric breakdown characteristics of metal oxide semiconductor capacitors. The deterioration of breakdown characteristics Strongly depends on ion species, dose, oxidation temperature, and oxidation ambient. The dielectric breakdown fields and charge to breakdown (Q(BD)) reduce drastically at doses of 5 x 10(13), 1 x 10(14), and 5 x 10(14) cm(-2) for the arsenic (As+), phosphorus (P+), and boron (B+) implantation, respectively. The breakdowns occur due to weak spots formed along the localized oxidation of silicon (LOGOS) edge by the combination of medium dose ion implantation, high temperature oxidation, and residual stress near the LOGOS edge.