Numerous nitridation processes have been studied to obtain very thin (≤ 6 nm), reproducible and reliable gate oxides. Recent results (1,2,3) have confirmed that i) the NO molecule is the species responsible for the nitrogen incorporation at the SiO2/Si interface and that ii) the direct use of NO gas allows the gate oxide to be nitrided at low thermal budget whilst maintaining the same advantages as those of N2O nitridation. NO nitridation of very thin oxides has so far been inadequately documented in terms of incorporated nitrogen concentration at the SiO2/Si interface. It is of prime importance to control the incorporation of a few nitrogen monolayers at the SiO2/Si interface, particularly for device performances in the 0. 18μm CMOS technology. In the following we present results on the control of low nitrogen concentration in pure NO atmosphere, with particular emphasis on a method based on the re-oxidation of nitrided oxides. This method can be used in a production line thus avoiding the high costs and long characterization times associated with SIMS measurements.