The presence of nitrogen in the dielectric films is known to impart highly desirable properties in the ultra-large-scale-integration era; the position, amount and concentration profiles of nitrogen are of great interest. In this work, we have studied two-step processes leading to bimodal nitrogen concentration profiles, with one nitrogen peak near the Si/dielectric interface and the other at the dielectric surface. Secondary Ion Mass Spectroscopy and Angled Resolved X-Ray Photoelectron Spectroscopy studies suggest that an ammonia nitridation step (at 1000 degreesC and 1 atm) following silicon oxynitridation in N2O (or possibly following oxidation in O-2) at the same conditions results in a bimodal nitrogen profile when short nitridation times are used; increasing the duration of the nitridation step is found to completely nitridate the initially grown oxynitride (or oxide). Post nitridation of NO-grown oxynitrides that are not found to result in bimodal N concentration profiles at the conditions studied. The experimental findings are in agreement with theoretical predictions of preliminary modeling studies. The engineering of desired bimodal nitrogen concentration profiles in nano-dielectric materials of interest becomes, therefore, possible through two-step processes. (C) 2003 Elsevier Science B.V. All rights reserved.