NOVELTY - Forming an aluminate (Al2O3)/silica (SiO2) stack comprises successively: (a) providing a substrate into a reaction chamber; (b) injecting into the reaction chamber at least one silicon containing compound; (c) injecting into the reaction chamber an oxygen source; (d) reacting at a temperature of 20-400 degrees C at least one of the silicon containing compounds and the oxygen source; (e) injecting on the silicon oxide film at least one aluminum containing compound; (f) injecting the oxygen source; (g) reacting at least one of the aluminum containing compounds and the oxygen source.    USE - The method is useful for forming an Al2O3/SiO2 stack, where the stack is useful for the passivation of photovoltaic devices, in particular for solar cells (all claimed).    ADVANTAGE - The method effectively forms an Al2O3/SiO2 stack which has a very efficient passivation for n-type and p-type substrates.    DETAILED DESCRIPTION - Forming an aluminate (Al2O3)/silica (SiO2) stack comprises successively: (a) providing a substrate into a reaction chamber; (b) injecting into the reaction chamber, through an atomic layer deposition (ALD) process, at least one silicon containing compound selected from: Bis(diethylamino)silane SiH2(Net2)2 (BDEAS), Bis(dimethylamino)silane SiH2(NMe2)2 (BDMAS), Bis(ethylmethylamino)silane SiH2(NEtMe)2 (BEMAS), (Di-isopropylamido)silane SiH3(NiPr2) (DIPAS), (Di tert-butylamido)silane SiH3(NtBu2) (DTBAS); (c) injecting into the reaction chamber an oxygen source selected in the list: oxygen, ozone, oxygen plasma, water, carbon dioxide (CO2) plasma, nitrogen oxide (N2O) plasma; (d) reacting at a temperature of 20-400 degrees C, preferably lower or equal to 250 degrees C, into the reaction chamber at least one of the silicon containing compounds and the oxygen source in order to obtain the SiO2 layer deposited onto the substrate; (e) injecting on the silicon oxide film, through an ALD process, at least one aluminum containing compound selected in the list: Al(Me)3, Al(Et)3, Al(Me)2(OiPr), Al(Me)2(NMe)2 or Al(Me)2(NEt)2; (f) injecting the oxygen source as defined in step (c); (g) reacting at a temperature comprised between 20 degrees C and 400 degrees C, preferably less than or equal to 250 degrees C, into the reaction chamber at least one of the aluminum containing compounds and the oxygen source in order to obtain the Al2O3 layer deposited onto the SiO2 layer issued of step (d). An INDEPENDENT CLAIM is Al2O3/SiO2 stack obtained according to the method.