The action or process of layers of something forming on a surface over a long period time: A deposition in geology can be explained as the spreading of sediments by a natural process.

A process of producing materials for semiconductors: Metal-organic chemical vapor depositions includ photovoltaic material, in which a surface layer is produced by the deposition on a substrate of a volatile organo-metallic compound; such as, methyl, which is transported to the surface through the gas phase at elevated temperatures.