Boron diffusion into Si from low-pressure chemical vapor deposition (LPCVD) borosilicate glass (BSG) by rapid thermal annealing (RTA) has been studied. The influence of native oxide between BSG and Si on doping characteristics is small for LPCVD BSG, while an unintentionally formed thin oxide between BSG and Si causes a rapid change in surface boron concentration at the initial stage of diffusion for atmospheric pre;;sure chemical vapor deposition BSG. Boron diffusion in Si is markedly enhanced for high-boron-concentration BSG. This is inherent to the BSG/Si structure, because enhanced diffusion is also observed for furnace annealing (FA). However, the enhancement is more pronounced. for RTA, indicating that enhanced diffusion originating from RTA occurs for the BSG/Si structure. The origin of the enhanced diffusion in RTA is not related to rapid heating but-to infrared light heating.