Ultra-low power SiGe HBT was developed for wide-range microwave applications. The key technologies of the SiGe HBT are based on well-controlled SiGe / Si epitaxial growth techniques with low-temperature chemical vapor deposition (CVD), which give several important features of the low-power SiGe HBT. The prominent features are a robustly designed n+-n --p+ emitter-base junction and a narrow base, realized by an epitaxially grown emitter and a low-temperature thermal cleaning prior to the emitter growth. These features were found to decrease both an emitter junction capacitance (CJE) and a carrier transit time in base (τB) in a great extent. The low-temperature CVD also contributed to the reduction of a collector junction capacitance (CJC) by controlling a mono-poly interface in the collector. The effective decrease of CJE, τB, and CJC has increased a cutoff frequency (fT) at a wide range of a collector current density (J C). As a result, Jc of the SiGe HBT decreased more than 60% compared to published data, at a wide fT range from 30 to 200 GHz. Index Terms - Heterojunction bipolar transistors, epitaxial growth, impurity profile, Si spacer, emitter capacitance, collector capacitance, corrector current density.