Very low energy (6 keV) BF+2 ion implantation has been used to form very shallow (≤1000 Å) junctions in crystalline and Ge+ preamorphized Si. Low‐temperature furnace annealing was used to regrow the crystal, and rapid thermal annealing was used for dopant activation and radiation damage removal. In preamorphized samples, Ge+ implantation parameters were found to have an influence on B diffusion. Our results show that for temperatures higher than 950 °C, B diffusion, rather than B channeling, becomes the dominant mechanism in determining the junction depth. Computer simulations of the profiles show regions of retarded and enhanced B diffusion, which depend on surface and end‐of‐range damage, respectively.