Current-voltage characteristics of ultrashallow p+-n and n+-p diodes, obtained using very low-energy (<500 eV) implantation of B and As, are presented. P+-N junctions were formed by implanting B+ ions into n-type Si (100) at 200 eV and at a dose of 6 x 1014 cm-2, and n+-p were obtained by implanting As+ ions into p-type (100) Si at 500 eV and at a dose of 4 x 1012 cm-2. A rapid thermal annealing (RTA) of 800°C/10 s was performed before I- V measurements. Using secondary ion mass spectrometry (SIMS) on samples in-situ capped with a 20-nm 28Si isotopic layer grown by low-energy (40 eV) ion-beam deposition (IBD) technique, the depth profiles of these junctions were estimated to be 40 and 20 nm for p +-n and n+-p junctions, respectively. These are the shallowest junctions reported in the literature. The results show that these diodes exhibit excellent I-V characteristics, with ideality factor of 1.1 and a reverse bias leakage current at -6 V of 8 x 10-12 and 2 x 10-11 A for p+-n and n+-p diodes, respectively, using a junction area of 1.96 x 10 -3 cm2.