We have compared the electrical characteristics and the depth profile of ultrashallow junctions formed by boron implantation at 0.5 keV and BF2 implantation at 2.2 keV. The modeling of the boron profile was performed using the Monte Carlo method for an as-implanted profile and the computationally efficient method for transient-enhanced diffusion. A junction depth of BF2 is shallower than that of boron after annealing. For an ultrashallow junction, HF dipping prior to rapid thermal annealing causes a significant loss of dopant and high sheet resistance. Considering the 0.1 μm metal–oxide–semiconductor field-effect transistor application, the optimizations of implantation and annealing conditions are necessary to satisfy the requirement of junction depth and sheet resistance. © 1999 American Institute of Physics.