Electron spin resonance (ESR) analysis reveals the incorporation of N in (100)Si/HfO2 structures with ultrathin amorphous HfO2 films deposited by chemical vapor deposition (CVD) using Hf(NO3)(4) as precursor, through detection, after Co-60 gamma-irradiation, of NO2 radicals (density greater than or similar to55 at. ppm). The molecules are found to be stabilized and likely homogeneously distributed in the HfO2 network. Some network forming N entity is suggested as a precursor, transformed into ESR-active NO2 upon gamma-irradiation. The interesting N incorporation aspect appears inherent to the particular CVD process. (C) 2004 American Institute of Physics.