Cluster-ion implantation in combination with two-step annealing is effective in making ultrashallow junctions. We have demonstrated the use of heavy atom-boron cluster ions to effectively reduce the boron energy for shallow-junction formation. SiB, SiB2, and GeB cluster ions have been used to produce 2 keV boron for low-energy ion implantation. We have generated the SiB, SiB2, and GeB cluster ions using the source of negative ions by cesium sputtering ion source. Shallow junctions have been made by SiB, SiB2, and GeB cluster ions implanted into Si substrates at 1 x 10(15)/cm(2) with energies at 6.88, 8.82, and 15 keV, respectively. We also discussed the benefit of a 550 degreesC preannealing before a 1000 degreesC, 10 s rapid thermal annealing.