The depth profile in nitrided SiO2 films using N-2 remote radio frequency plasma was investigated. N was incorporated into the film at levels of up to 27 atom %, largely concentrated at the film surface, and not the film interface. The depth profiling data showed that the depth of incorporated N is dependant on film thickness, i.e., N is incorporated to a depth of about 1.1 nm in a 1.5 nm thick film, while the depth is significantly less to about 0.7 nm in the case of a 4.0 nm thick film. Moreover, under the same nitridation condition, more N content is concentrated nearer to the surface of a 1.5 nm thick oxide film than that of 4.0 nm thick film. N-2, generated in the molecule during the nitrogen process is almost completely concentrated at the film interface. After an additional annealing treatment, the molecular N-2 diffuses out extensively and N, which is chemically bonded to Si-3, is changed into a more stable state with different second-nearest neighbors, accompanied by reoxidation at the film interface of an ultrathin film. (c) 2006 The Electrochemical Society.