Arsenic and phosphorus codiffusion was studied using a buried boron layer. Analysis of the dopant profiles was performed using secondary ion mass spectroscopy, spreading resistance profiles, and junction staining. Contrary to expectations, the profiles of arsenic and phosphorus diffused by themselves were enhanced over the codiffused profiles. The buried boron profile in the case of phosphorus alone was enhanced over the boron profile in the case of arsenic and phosphorus codiffusion. The residual annealing of implantation damage is thought to be responsible for these effects. In addition, the suppression of the self‐interstitial supersaturation for codiffused conditions is a transient effect and is postulated to be caused by an increase in recombination of implantation‐generated vacancies and self‐interstitials due to the presence of a high concentration of arsenic atoms.