A detailed review of SiGe epitaxial base technology is presented, which chronicles the progression of research from materials deposition through device and integration demonstrations, culminating in the first SiGe integrated circuit application. In part I of this paper, the requirements and processes for high-quality SiGe film preparation are discussed, with emphasis on fundamental principles. A detailed overview of SiGe HBT device design and implications for circuit applications is then presented. In part II, process integration concerns are described, first in general terms, followed by an extensive review of simple, nonself-aligned device structures, and lastly, a review of more complex self-aligned structures. The extension of SiGe device technology to high levels of integration is then discussed through detailed review of a full SiGe-HBT BiCMOS process. Finally, the successful fabrication of a 12-bit Digital-to -Analog Converter is presented to highlight the application of SiGe technology.