Field emitters have high-speed response characteristics at over 100 GHz because they utilize electron emission in a vacuum. Therefore, field emission devices are very suitable for use as high-speed switching elements. Practical field emitters can be fabricated by using the Si process. Consequently, the authors have fabricated a local vacuum package on a Si substrate that is adapted to the integrated circuit process for on-chip integrated devices. The technique was then used to fabricate Si field emitter arrays with integrated circuits on Si substrates. This has the great advantage that devices can be aligned on a micrometer size. This technique is very useful for many applications involving high performance on-chip integrated devices.