A method of growing a thin film comprises growing a thin film by conformally forming at least one layer over a substrate having structures extending from a surface of the substrate, whereby the or each layer is formed over the surface of the substrate and over the structures extending from the surface. The thickness of the conformal layer, or the sum of the thicknesses of the conformal layers, is at least half the average spacing of the structures, and; at least one of the height of the structures, the average spacing of the structures and the size of the smallest dimension of the structures is set so as to provide an enhanced growth rate for the or each conformal layer (compared to the growth rate over a planar substrate).