The low and high-frequency noise of high-speed/high-frequency noise characteristics of semiconductor devices are reviewed. The devices reported include High-Electron Mobility Transistors (HEMTs) and Heterojunction Bipolar Transistors (HBTs). Different heterojunction designs based on various material systems are investigated such as, AlGaAs/GaAs, GaInP/GaAs, InAlAs/InGaAs and InP/InGaAs. The noise features of each design are reviewed and the origin of noise is analyzed. The relation of low-frequency noise to reliability characteristics of HBTs is also addressed.