Oxynitride gate dielectric and method of forming

The present invention generally relates to a gate dielectric for a semiconductor device and method of forming and more particularly, relates to an oxynitride gate dielectric structure that contains nitrided regions with controlled concentrations of nitrogen for use in a semiconductor device and method of forming the structure. A method for forming an oxynitride gate dielectric in a semiconductor device and gate dielectric structure formed by the method are disclosed. In the method, an oxynitride layer is first formed on a silicon surface and then re-oxidized with a gas mixture containing oxygen and at least one halogenated species such that an oxynitride layer with a controlled nitrogen profile and a layer of substantially silicon dioxide formed underneath the oxynitride film is obtained. The oxynitride film layer can be formed by either contacting a surface of silicon with at least one gas that contains. nitrogen and/or oxygen at a temperature of not less than 500° C. or by a chemical vapor deposition technique. The re-oxidation process may be carried out by a thermal process in an oxidizing halogenated atmosphere containing oxygen and a halogenated species such as HCl, CHCl, CHCl, CHCl. CHCl and CHCl.