Monocrystalline silicon was implanted with 60 keV fluorine and 20 keV boron ions and annealed. Carrier profile, fluorine and boron redistribution, and the parameters ofp+-njunctions were investigated. In ion implanted Si two specific regions were observed in which peculiarities in carrier concentration, resistivity, and F atoms redistribution occurred. It was reasoned that the “under-surface” specific region is enriched with vacancy-type defects while the “amorphous/crystalline(a/c)interface” region is enriched with interstitial type defects. After annealing at a temperature corresponding to the reverse annealing phenomenon, boron atoms were activated in the “under-surface” and deactivated in the “a/cinterface” region. The possibility of PMOS transistor fabrication with ultrashallowp+-njunction (60 nm) and low leakage current byF++B+implantation and low temperature (600–700) °C annealing by using this phenomenon was demonstrated. ©1997 American Institute of Physics.