A new technique for nanometer-scale gap formation was proposed and investigated for the possibility in vacuum microelectronic device application. When the temperature is down at the end of oxidation, the compressive stress induced at the initially connected slim polysilicon patterns forces to be separated into two parts, yielding wedge-shaped cathode and anode tips for a field emission array with extremely small interelectrode distance. The oxidation time and the polysilicon thickness are the key parameters to control the interelectrode gap. The fabricated field emission devices show very high emission current with low turn-on voltage.