We report on an ultra-high vacuum (UHV) compatible method for fabricating devices of sub-micrometer size by virtue of a non-organic evaporation mask of high thermal and mechanical stability. As an application we describe the superconducting properties of mesoscopic superconductor/normal-metal and superconductor/ferromagnet/superconductor hybrid structures. In particular, we report on the observation of the DC-Josephson effect in Nb/Cu/Co/Cu/Nb structures prepared in UHV. The Josephson coupling between the two superconductors through the very thin (5 nm) magnetic and metallic weak link is confirmed by the magnetic field dependence of the critical current I-c, which displays a Fraunhofer-like interference pattern. (C) 2002 Elsevier Science B.V. All rights reserved.