We report on a fabrication process that uses SOI substrates and micromachining techniques to form wide-IF SIS mixer devices that have suspended metal beam leads for rf grounding. The mixers are formed on thin 25 mum membranes of Si, and are designed to operate in the 200-300 GHz band. Potential applications are in tropospheric chemistry, where increased sensitivity detectors and wide-IF bandwidth receivers are desired. They will also be useful in astrophysics to monitor absorption lines for CO at 230 GHz to study distant, highly redshifted galaxies by reducing scan times. Aside from a description of the fabrication process, electrical measurements of these Nb/Al-AIN(x)/Nb trilayer devices will also be presented. Since device quality is sensitive to thermal excursions, the new beam lead process appears to be compatible with conventional SIS device fabrication technology. (C) 2004 American Vacuum Society.