NOVELTY - The process comprises applying a 0.5-50 nm-thick film of an organic polymer, an inorganic film, an inorganic-organic hybrid material, alucone or a zinc-ethylene glycol hybrid material (zinc alkoxide) or a titanium-ethylene glycol (titanium alkoxide) hybrid material to a portion of a surface of a substrate via an atomic layer deposition process, and subjecting the organic polymer or inorganic-organic hybrid film to reaction conditions such that pores are formed in the film. The pores are produced by oxidization, reduction, hydrolysis, pyrolysis, decomposition or other chemical reaction.    USE - The process is useful for producing a porous film on a substrate such as micro-electro-mechanical system device or sensor, where the film is useful in high flux/selectivity membranes that are useful in water desalination, gas separation and selective proton/oxygen conduction in fuel cells.    ADVANTAGE - The process is capable of effectively and controllably producing the ultra-thin porous film on the substrate such as micro-electro-mechanical system device or sensor thus enhancing the selectivity of the sensor.    DETAILED DESCRIPTION - The process comprises applying a 0.5-50 nm-thick film of an organic polymer, an inorganic film, an inorganic-organic hybrid material, alucone or a zinc-ethylene glycol hybrid material (zinc alkoxide) or a titanium-ethylene glycol (titanium alkoxide) hybrid material to a portion of a surface of a substrate via an atomic layer deposition process, and subjecting the organic polymer or inorganic-organic hybrid film to reaction conditions such that pores are formed in the film. The pores are produced by oxidization, reduction, hydrolysis, pyrolysis, decomposition or some other chemical reaction. The porous film has a thickness of 0-30 nm and a surface area of 100 m2/g, and is essentially free of pores having widths of greater than 1000 angstroms. The substrate material is or contains catalytic material; a reagent for a chemical reaction; a porous material, which functions as a support for a membrane or filtration device; a pharmaceutical or nutrient; or a micro-electro-mechanical system device or sensor. INDEPENDENT CLAIMS are included for:    (1) a substrate having a coating of a porous film;    (2) a coated substrate;    (3) a process for conducting a chemical reaction in the coated substrate; and    (4) a method of delivering a pharmaceutical or nutrient to a living organism.    DESCRIPTION OF DRAWING(S) - The diagram shows a graph indicating the distribution of micropores on a water-treated alucone film.