Structure and method are provided for forming a bipolar transistor. As disclosed, an intrinsic base layer is provided overlying a collector layer. A low-capacitance region is disposed laterally adjacent the collector layer. The low-capacitance region includes at least one of a dielectric region and a void disposed in an undercut underlying the intrinsic base layer. An emitter layer overlies the intrinsic base layer, and a raised extrinsic base layer overlies the intrinsic base layer.