The disclosure provides bipolar transistor structures with sloped base sidewalls and related methods to form the same. A structure according to the disclosure includes an intrinsic base on a collector and having an emitter thereon. A first extrinsic base is on the intrinsic base, and the first extrinsic base includes a sloped sidewall substantially aligned with a sloped sidewall of the intrinsic base. A first extrinsic includes a sloped sidewall substantially aligned with a sloped sidewall of the intrinsic base. A second extrinsic base has a sloped sidewall on and adjacent the sloped sidewall of the intrinsic base.