The structure of a high-speed self-aligned SiGe heterojunction bipolar transistor (HBT) was optimized through investigations of its characteristics related to the collector-base and emitter-base junctions. The SiGe HBT was fabricated by selective-epitaxial growth (SEG). As a result of the optimization, its cutoff frequency was increased to 130 GHz and its ECL gate-delay time was reduced to 5.3 ps. Based on this SiGe HBT, an IC chipset for 40 Gb/s optical-fiber-links, a 5.8 GHz electronic-toll-collection transceiver IC, and high-speed frequency divider ICs (operating up to the millimeter-wave band) were developed. (C) 2003 Elsevier B.V. All rights reserved.