Cold‐cathode microdiodes with tungsten and heavily doped polycrystalline silicon emitters have been fabricated using silicon planar processing and solid‐state surface micromachining techniques. This work has focused on building reliability into vacuum microelectronic devices and eliminating the need for external vacuum pumping as commonly used in these devices. The following technology advances have been incorporated into sealed microdiode devices: (1) recessed cavities with lateral chemical etch delivery channels, (2) electron beam‐evaporated vacuum enclosures, (3) the use of atomic force microscopy to analyze the fine grain emitter surface structure, (4) the use of soft x‐ray photoelectron spectroscopy to determine surface chemical composition of cathode and anode surfaces, and (5) the use of ultraviolet photoelectron spectroscopy to measure as‐processed work function.