A vacuum has several advantages over a solid as an electron transport medium. However, conventional vacuum devices have several disadvantages such as large size and high power consumption because thermal cathodes are used. Recent micro- or nano-fabrication technology enables the development of functional field emitter arrays such as field emitters monolithically incorporating a vertical-type field effect transistor and field emitters with an electro-static lens. In this paper I introduce these functional field emitter arrays and the vacuum nanoelectronics devices which are being developed. I describe the expectation to vacuum nanoelectronics which provide compact, stable at harsh conditions, and high frequency/power output.
