SiGe (/ˈsɪɡiː/ or /ˈsaɪdʒiː/), or silicon-germanium, is an alloy with any molar ratio of silicon and germanium, i.e. with a molecular formula of the form Si_1−xGe_x. It is commonly used as a semiconductor material in integrated circuits (ICs) for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors. IBM introduced the technology into mainstream manufacturing in 1989. This relatively new technology offers opportunities in mixed-signal circuit and analog circuit IC design and manufacture.