The necessity to decrease silicon wafer-processing temperatures substantially has stimulated research into new and innovative techniques for the formation of thin dielectric films. A photo-decomposition technique using Nitric Oxide (NO) is one such promising method. Thermally NO-grown and NO-annealed dielectric films have already shown very encouraging physical and electrical results. This study compares thermally NO-grown oxides with thermally NO grown and assisted by ultraviolet (UV) irradiation. Methods using UV and vacuum UV light generated from low-pressure mercury or deuterium lamps to stimulate the growth of ultrathin dielectric films are described. The oxynitridation of silicon is carried out by irradiating an ultraviolet beam on the heated silicon substrate covered by a thin layer of nitric oxide gas. Typical resultant film thickness were in the range 10 –40 A after oxynitridation for various times at 500°C. MIS devices were fabricated using these films as gate insulators and were electrically characterized. Electrical characterization revealed good film qualities, rendering this new UV-NO oxynitridation technique promising for low temperature (<600°C) semiconductor processing. Films grown in NO ambient under deuterium lamp irradiation followed by NO annealing were also investigated. These results will also be presented.