The fabrication of mixer diodes for use at millimeter-wave frequencies requires the definition of extremely small area Schottky-barrier junctions. It is not a trivial matter to fabricate such devices at low cost which simultaneously are mechanically rugged, exhibit low parasitics, and present high figures of merit. This paper presents a novel technology for accomplishing these objectives. By incorporating "shadow masked" proton bombardment and metal evaporation, planar beam-leaded devices of low capacitance are realized in the absence of the critical processing steps which have traditionally resulted in low yields. GaAs devices having zero bias capacitance of 0.06 pF are obtained with a series resistance of less than 3 Ω giving a cutoff frequency in excess of 800 GHz. Initial RF tests have resulted in a noise figure and conversion loss of 5.8 and 3.8 dB, respectively, at 10.7 GHz. This technology should result in the availability of inexpensive GaAs mixer diodes suitable for use at millimeter-wave frequencies.