One of the candidates for the Oxyde-Nitride-Oxyde replacement in next generations Flash Non Volatile Memories is aluminum oxide deposited by Atomic Layer Deposition, which guarantees excellent film conformality, a feasible dielectric constant and low leakage current (1). Al2O3 films are grown in an ALD reactor at 300 {degree sign} C using Trimethylaluminium and H2O as precursors. The impact of NH3 and O2 post deposition treatments on Al2O3 thermal stability up to N2 Rapid Thermal Process (RTP) at 1030 {degree sign} C has been investigated. After RTP, while the O2 treatment prevents N incorporation and does not induce any crystallographic modification of the Al2O3 layer, the NH3 treatment causes an increase of the N content in the film and induces a reduction of the preferential orientation of the crystallized Al2O3 grains. Actually, the crystallization on set temperature is shifted to higher temperatures …