Excellent shallow p+n junctions have been formed by implanting BF+2 ions into thin polycrystalline Si films and subsequent annealing. The samples implanted with 5×1015 cm -2 at 50 keV show a leakage of 1 nA/cm2 and a junction depth of about 0.05 μm after a 800°C annealing. Various implant and annealing cases were examined to determine and characterize their effects on the resultant junctions. High energy implantations (125 and 150 keV) exhibit poor characteristics at all annealing temperatures because the Si substrates are severely damaged. However, the specimens implanted below 100 keV result in excellent diode characteristics for all implantation doses after an 800°C annealing since the implantation defects are confined in the poly-Si layer. The major factors affecting the junction depth were found to be the implantation energy and annealing temperature, while a minor for the implantation dosage. Furthermore, the effects of the subsequent silicidation on the resultant junction characteristics were also investigated.