The present invention relates to a deposition process for thin film deposition onto a substrate comprising providing a plurality of gaseous materials comprising at least first, second, and third gaseous materials, wherein the first and second gaseous materials are reactive with each other such that when one of the first or second gaseous materials are on the surface of the substrate the other of the first or second gaseous materials will react to deposit a layer of material on the substrate and wherein the third gaseous material is inert with respect to reacting with the first or second gaseous materials. The process comprises flowing the gaseous materials along the length direction of a plurality of elongated channels across the surface of the substrate surface in close proximity thereto.