Over the past three decades the driving force behind the expansion of the microelectronics industry has been the ability to pack ever more features onto a silicon chip, achieved by continually miniaturising the size of the individual components. However, after 2015 there is no known technological route to reduce device sizes below 10nm. We demonstrate a radical new technology for atomic-scale (0.1nm) device fabrication in silicon using a combination of scanning tunnelling microscopy and atomic precision crystal growth. In particular we focus on the ability to place individual phosphorus atoms in silicon at precise locations and encapsulate them in epitaxial silicon with minimal diffusion and segregation of the dopants. We present results demonstrating the power of this approach both towards the controlled fabrication of atomic-scale devices in silicon, and towards the construction of a solid-state silicon based quantum computer.