Low energy ion implantation and low-temperature microwave annealing were used in this study to fabricate ultra-shallow junctions (USJs). A two-steps modulatory microwave annealing (MWA) process was employed to recover and activate a boron (400 eV) implanted silicon wafer. In the first step, 2.4 kW high power MWA was used to regrow an amorphous layer with the crystal silicon phase and thus enhance MWA absorption. After crystal silicon regrowth, 0.6 kW low power MWA was used to activate the implanted boron. The SIMS profile shows that the junction depth @5e18 was 13.5 nm, which is able to meet the requirement of the 20 nm VLSI process. The current on/off ratio (I-on/off) of the P-MOS device is higher than 10(6) (V-DS = -0.05 V). The device subjected to two-steps MWA at 2400 W for 300 s + 600 W for 600 s had the lowest Vth. It also had the lowest subthreshold swing (SS), which means that it was best able to control the leakage current.