In this paper, the authors investigate the impact of device interconnect parasitics on the two most commonly-accepted RF small-signal figures-of-merit, the transit frequency (fT) and the maximum frequency of oscillation (fmax) in state-of-the-art SiGe HBT technology. Simulations and measurement results are provided as a guideline to design an optimum device interconnect scheme to achieve a high fmax. Test structures were characterized with de-embedding structures providing reference planes at the device level and at the top-metal level. Measurements show an fmax of 450 GHz at the device level and at the top-metal level a degradation of only 4% to 430 GHz. These results demonstrate a significant advantage of the SiGe HBT technology compared to ultra-scaled CMOS technology at device speeds approaching a terahertz, and to the best of the authors' knowledge, demonstrate the highest fmax reported at the top-metal level in any state-of-the-art silicon technology.