The invention provides for an alternative and less complex method of manufacturing a bipolar transistor comprising a field plate (17) in a trench (7) adjacent to a collector region (21), which field plate (17) employs a reduced surface field (Resurf) effect. The Resurf effect reshapes the electric field distribution in the collector region (21) such that for the same collector-base breakdown voltage the doping concentration of the collector region (21) can effectively be increased resulting in a reduced collector resistance and hence an increased bipolar transistor speed. The method comprises a step of forming a base window (6) in a first base layer (4) thereby exposing a top surface of the collector region (21) and a part of an isolation region (3). The trench (7) is formed by removing the exposed part of the isolation region (3), after which isolation layers (9,10) are formed on the surface of the trench (7). A second base layer (13) is formed on the isolation layer (10), thereby forming the field plate (17), on the top surface of the collector region (21), thereby forming a base region (31), and on a sidewall of the first base layer (4), thereby forming an electrical connection between the first base layer (4), the base region (31) and the field plate (17). An emitter region (41) is formed on a top part of the base region (31), thereby forming the Resurf bipolar transistor.