Advances in the science and technology of thin films, interfaces, and heterojunctions have revolutionized research programs oriented towards high speed computation and telecommunication. For some material systems, it is now possible to form heterojunctions with little or no constraints by the lattice parameter of the host semiconductor. The ability to synthesize and tailor the structure of heterojunction thin films has already led to the fastest transistor with the oscillation frequencies well over 200 GHz and smallest noise contribution. These heterojunction systems require expertise in semiconductor physics, material science and device engineering. Concepts, technologies, performance and fundamental issues of high speed devices are reviewed. Among the devices treated are the modulation doped conventional AlxGal, As/GaAs, pseudomorphic AlxGai, As/ [fixGal, As and new InxAl-xAs/ InxGa1-x As (lattice matched to InP) heterojunction field effect transistors (MODFETs), and the AlxGa1-x As/GaAs heterojunction bipolar transistors (HBTs). Lattice and thermal mismatch induced strain effects on the performance of high speed devices are discussed.