The incorporation of N atoms during the deposition of thin HfO 2 films on (100)Si through NCVD using the Hf(NO 3) 4 was analyzed using electron spin resonance measurements. The centers appearing upon γ-irradiation were identified as embedded NO 2 radicals. The molecules were stabilized and homogenously distributed in the HfO 2 network. The N incorporation appeared inherent to the particular NCVD process. The network forming N entity was found to be a precursor, transformed into ESR-active NO 2 upon γ-irradiation.