As the top Si layer is thinned, the dopants' diffusion in the confined Si layer in SOI wafer with respect to different thermal treatments needs to be better understood. Boron, BF2 with/without Ge pre-amorphization were implanted into bulk Si and SOI wafers with 530 Å Si and 1475A BOX. Samples were annealed using both spike (Impulse) anneal and Flash anneal. Simulations of dopant diffusion is used to resolve apparent differences in dopant profiles that resulted for SOI in contrast with bulk Si samples. Result suggests that the implantation damage difference between SOI and bulk Si makes the B diffusion in SOI higher than in bulk Si.