We report the first direct observation of dissociative chemisorption of oxygen molecules on a silicon surface at room temperature via a molecular precursor state. We link this to the fact that smooth oxide layers can be grown easily on Si(113). The process of initial oxidation is discussed in terms of surface diffusion paths and surface stress. First ab initio calculations elucidate the favored adsorption sites and the oxidation mechanism. Experimental evidence indicates bond geometries that lead to the quasi-epitaxial growth of an extremely thin SiO2 layer on the substrate at elevated temperatures (600 degreesC). In contrast to Si(001) oxidation, neither defects nor the ejection of Si atoms plays a significant role during the initial oxidation of Si(113). Gate-controlled diodes prepared on Si(113) and Si(001) 4-in. wafers under optimized conditions for Si(001) show no significant differences in the density of rechargeable interface states, threshold voltages, and charge carrier generation and recombination.