The which edge is embedded in an insulating intermediate layer which affects the electric charge in adjacent surface region of the semiconductor substrate. The electrode is mounted on an oxide film (4) on the substrate (2). - The surface part of the substrate surrounded by the intermediate layer (6) is covered by the metal electrode (10). The intermediate layer covers also the oxide film whose surface charge is sufficiently increased by suitable pretreatment of the substrate, to compensate the charge carrier enrichment in the substrate semiconductor layer adjacent to the intermediate layer.
