A process for producing a monomolecular built-up film of monomolecular layers of a silane surfactant is described. In the process, the silane surfactant is chemically adsorbed on a hydrophilic surface of a substrate and is subjected to irradiation of a high energy beam or plasma treatment in an active gas atmosphere to activate the monomolecular layer. This activated layer is further adsorbed with the silane surfactant to form a built-up film. The beam irradiation or plasma treatment may be effected in a desired pattern. The beam irradiation or plasma treatment and the further adsorption are repeated until the desired number of the monomolecular layers is obtained.