Abstract: A bipolar junction transistor (BJT) comprising a semiconductor region and a plurality of metal contacts, located on a top surface of the semiconductor region, where the plurality of metal contacts comprise one or more first metal contacts that are in contact with one or more emitter regions and one or more second metal contacts that are in contact with an upper surface of a body region of the semiconductor region. One or more insulating structures are located on the top surface of the semiconductor region, where the insulating structures isolate the one or more first metal contacts from the one or more second metal contacts. A metal layer is located over the insulating structures, where the metal layer is in contact with one or more first metal contacts and is isolated from the one or more second metal contacts by the insulating structures.

Abstract: A semiconductor device, comprising a trench extending into the device from a surface. The trench has sidewalls extending along the length of the trench, a depth and a width defined at said surface between said sidewalls. The trench is at least partly filled with a material. At least one of the sidewalls is provided with at least one lateral recess, the or each recess providing a discrete localised increase in said trench width.