Abstract: A high-frequency transistor having a substrate of a first conductivity type, an epitaxial collector layer of the first conductivity type, a layer-shaped base region of the second opposite conductivity type, which is provided in the collector layer and is subdivided by a sunken oxide pattern into a number of base zones which are interconnected by conducting layers located on the oxide pattern, and at least one emitter zone of the first conductivity type in each base zone. According to the invention, the conducting layers consist of poly-crystalline silicon of which an edge is covered with a thin oxide layer which extends into the base zone and laterally bounds the emitter zones.

Abstract: By the use of high-ohmic polycrystalline silicon(poly) in MIS elements, a depletion layer can be formed in the poly material which brings about an electric decoupling between the poly (gate) and the underlying semiconductor body. This effect can be utilized advantageously in various circuit elements, such as in CCD's, in order to obtain a favorable potential distribution in the substrate; in MOS transistors in order to reduce the parasitic capacities; and in high-voltage devices in order to increase the breakdown voltage at the edge of the field plate (resurf).

Abstract: A semiconductor device of the "RESURF" type has a substrate region and a superimposed semiconductor layer which forms a p-n junction with the substrate region. The semiconductor layer has an island-shaped region which is depleted at least locally up to the surface at a reverse voltage applied across the p-n junction which is well below the breakdown voltage of the p-n junction. According to the invention the island-shaped part of the semiconductor layer over at least a part of its area has a doping profile in the vertical direction with at least two overlying layer portions with different average net doping concentrations and of the same or opposite conductivity type, so as to increase the current-carrying capacity of the semiconductor layer.