The invention relates to a method for preparing thin layers of inorganic oxides on substrates by means of plasma-assisted vapour phase deposition. The inventive method is different from other common methods in that organic layer deposition steps are included between the successive inorganic oxide deposition steps such that, during the inorganic layer deposition step, the previously-deposited organic part is eliminated by combustion. Said method is suitable for developing selective membranes that are used to separate and purify fluids and to produce and modify sensors for gases and humidity and electronic components