A simple microtriode with planar field emission cathode is investigated. Electron optical performance and field distribution are simulated using numerical electron optics. A field emitter tip is fabricated by direct write nanolithography with electron beam induced deposition. The emission properties are studied in UHV and high vacuum. Measurements of currents from deposited emitters are recorded with milli-second resolution to monitor short-term variations in long-term measurements. Emission currents of a few nanoamperes are observed over several days without and with the use of an ion mirror. Depending on vacuum conditions the currents show a characteristic variation of up to 50%. The work is aimed to develop a planar micro-triode with very high current-carrying capability and low transconductance. (c) 2005 American Vacuum Society.