The design, fabrication and characterization of Micro-electro-mechanical metal-air-insulator-semiconductor (MEM-MAIS) diode switch are originally reported. An abrupt switching from off-state to Fowler-Nordheim tunneling current in on-state is induced by the electromechanical bi-stability of the structure. Electromechanical pull-in and pull-out events define a hysteresis window that can be exploited in the future for memory applications, if the device scaling and charging problems are properly addressed. Ultra low leakage currents in the off state due to in-series air-gap (~10 fA for 10 × 20 [mu]m2) and quasi-exponential on-current characteristics have been measured for devices with different spring constants.