This paper reports on a high-speed silicon bipolar transistor with an fT and fMAX of over 40 GHz, we call it the Advanced Boro-silicated-glass Self-Aligned (A-BSA) transistor. In basic BSA technology, a CVD-BSG film is used not only as a diffusion source to form the intrinsic base and the link base regions but also as a sidewall spacer between the emitter and the base polysilicon electrodes. An A-BSA transistor offers three advancements to this technology: (1) a graded collector profile underneath the intrinsic base region to suppress the Kirk effect; (2) an optimized design of the link base region to prevent the frade-off effect between fT and base resistance; and (3) a newly developed buried emitter electrode structure, consisting of an N++-polysilicon layer, a platinum silicide layer, and a CVD tungsten plug, to prevent the emitter plug effect. Furthermore, our transistor uses a BPSG filled trench isolation to reduce parasitic capacitance and improve circuit performance. In this paper, we describe device design, process technology and characterization of the A-BSA transistor, with it we have performed several application ICs, operating at 10Gb/s and above. The A-BSA transistor achieved an fT of 41 GHz and an fMAX of 44 GHz under optimized conditions.