Shrinking device dimensions have affected the interconnect performance leading to replacement of Al with Cu and investigations of a variety of low-K materials to replace SiO@sub 2@ and of other modes (e.g. optical) of signal transmissions between devices and devices and the outside world. As the surface-to-volume ratio increases, the surfaces and interfaces will control the properties and reliability of the interconnection and dielectric materials. In this paper, we will review and discuss the science and technology of interconnections for semiconductor circuits and the impact of surfaces and interfaces on their performance.