Point defect engineering using high-energy ion bombardment can be used as a method to inject vacancies near the surface region with excessive interstitials created near the end of the projected range deep inside the substrate. We demonstrate that implantation of MeV Si ions into a Si substrate can suppress boride-enhanced diffusion normally associated with a high B concentration layer. B atoms from a surface-deposited boron layer experienced a suppressed diffusion during annealing if the Si substrate was preimplanted with MeV Si ions, and the retardation of B diffusion became more effective with higher dosages. The concept of boron diffusion control was used as an approach to form ultrashallow junctions. (C) 2002 The Electrochemical Society.