The dimensions of semiconductor devices can now be reduced to the point where quantum-mechanical effects must be considered in device performance. New device concepts have therefore been proposed, and already realised, in which quantum-mechanical effects are used to achieve increased electron mobilities or in which interference phenomena are utilised. At present, the major drawbacks of nonoelectronics are the technological problems of realising the devices. The emphasis of this paper is on new technological concepts for device realisation. Additionally, an overview of proposed and realised devices is given. Future advances in nanofabrication may come from the development of the scanning tunnelling microscope and related systems.