Abstract: A method for forming an oxide layer on an electronic substrate such as a process of forming an ultra-thin gate oxide layer on a silicon wafer and an apparatus for executing for such method are provided. In the method, a moisture generator is continuously heated after a water vapor generating process is completed in order to prevent any residual moisture from condensing on an inner wall of the moisture generator. The method thus prevents additional water vapor from being communicated to an oxidation furnace and causing a continuous, undesirable growth of oxide on the wafers. The method may further be improved by flowing an inert gas into the oxidation chamber at a location adjacent to the oxidation chamber such that a substantially moisture-free inert gas flow may be flown into the chamber to improve the temperature uniformity in the chamber and to pressurize the chamber for preventing moisture or other contaminating gases from entering the chamber from the outside ambient.