NOVELTY - A fuel cell device is formed by providing a first and a second silicon substrate; forming in a first surface of the first and second substrates a gas delivery tunnel(s); forming a first and a second catalyst layer in electrical contact with the first and second substrate, respectively; forming a proton exchange membrane on the first catalyst layer; and assembling the first and second substrates.    USE - For formation of fuel cell device, useful in small portable devices, e.g. laptop computers and cellular phones.    ADVANTAGE - The use of silicon attains the possibility to utilize micromachining and lithographic techniques, to form the desired structures and to integrate the fuel cell with silicon-based control circuitry. The invention achieves simpler, smaller fuel cell, in contrast to, e.g. morse fuel cell, supra, in which the silicon is only a structural component, on which a separate metal anode current collector must be formed. The porous silicon gas diffusion regions provide a large surface area, over which gas diffusion from the tunnels onto the catalyst layer occurs, as compared to use of, e.g. a metal or other film with holes etched in it. With the use of monolithic structure and because of the exposed surface, simpler fabrication and improved control of the system hydration is achieved.    DETAILED DESCRIPTION - Formation of a fuel cell device, comprises: providing a first silicon substrate (30); forming in a first surface of the first silicon substrate, a gas delivery tunnel(s) (36, 54); forming a first catalyst layer (38) in electrical contact with the first silicon substrate; forming a proton exchange membrane (40) on the first catalyst layer; providing a second silicon substrate; forming in a first surface of the second silicon substrate, a gas delivery tunnel(s); forming a second catalyst layer (52) in electrical contact with the second substrate; and assembling the first and second silicon substrates, such that the second catalyst layer is brought into contact with the surface of the proton exchange membrane opposite the surface of the proton exchange membrane in contact with the first catalyst layer.    DESCRIPTION OF DRAWING(S) - The figure illustrates the formation of a fuel cell.    Substrate (30)    Porous silicon regions (32, 56)    Gas delivery tunnels (36, 54)    First catalyst layer (38)    Proton exchange membrane (40)    Second catalyst layer (52)