Abstract: The method in accordance with the invention is used for the production of field-effect transistors and preferably implemented in such a manner that a thin aluminum layer (2) is deposited on the surface of a silicon substrate (1), for example, by means of a basic cleaning solution containing aluminum, that subsequently thermal oxidation is effected, during which, in addition to a silicon dioxide layer (3), an about 1 to 1.5 nm thick layer (4) containing aluminum oxide and silicon dioxide is formed and that finally, if required, at least one further layer, for example, an Si.sub.3 N.sub.4 (5) or an Si.sub.3 N.sub.4 (5) and an SiO.sub.2 layer are deposited. By adding about 400 ppb aluminum to the cleaning solution, which in the finished structure equals a quantity of aluminum of about 250 pg/cm.sup.2 layer surface, the threshold voltage V.sub.S is raised by about 470 millivolts.

Abstract: A method for manufacturing a power transistor having a highly doped emitter zone and a narrow base zone with a flat doping profile.In a long-term diffusion step ensuring the flat doping profile, the base zone is diffused into a lowly doped substrate serving as a collector. In a subsequent etching process, the base zone is etched down to a shell-shaped remainder. A large area, highly doped emitter zone with a steep doping profile and thus a high emitter efficiency is introduced into this shell-shaped remainder in a short-term diffusion step.