Ultra-low-power and high-speed SiGe base bipolar transistors that can be used in RF sections of multi-GHz telecommunication systems have been developed. The SiGe base and a poly-Si/SiGe base-contact were formed by selective growth in a self-aligned manner. The transistors have a very small base-collector capacitance (below 1 fF for an emitter area of 0.2 x 0.7 /urn) and exhibit a high maximum oscillation frequency (30-70 GHz) at low current (5-100 /iA). The power-delay product of an ECL ring oscillator is only 5.1 fj/gate for a 250-mV voltage swing. The maximum toggle frequency of a one-eigth static divider is 4.7 GHz at a switching current of 68 /uA/FF.
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