The use of electron and ion beams in the field of microelectronics has grown rapidly over the past ten years. For example, fine-focused electron beams, which initially were employed in diagnostic tests on integrated circuits and semiconductor devices, now are being utilized in the laboratory for creating devices and circuits with resolutions considerably higher than the values achievable by photolithography, and ion beams are being employed in the production of integrated circuits. It is seen that the beam approach offers a number of advantages compared with contemporary techniques. This article describes some of the devices that can be fabricated with electron beams, thus indicating the state of the art, discusses the advantageous features of ion implantation doping, and points out the limitations on beam processes imposed by fundamental electron/ion optical effects.