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This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (fT) of 207 GHz and an fmax extrapolated from Mason's unilateral gain of 285 GHz. fmax extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm2 have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm2). Smaller transistors (0.12×0.5 μm2) have an fT of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 k/spl Omega//sq. and an open-base breakdown voltage BV/sub CEO/ of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting fT at small lateral dimensions.