Room temperature Si ion implantation and solid-phase epitaxial regrowth are used to improve the crystalline quality of SOS wafers. Several thickness (0.3 μm to 0.67 μm) SOS wafers are used for the investigation of the mechanism and kinetics of solid-phase epitaxial regrowth after amorphization of the Si layer. MeV helium backscattering with channeling technique, X-ray rocking curve and TEM analysis indicate that a significant reduction in the defect density is obtained for thinner SOS wafers. An annealing time of 2 hrs at 950°C is found to be sufficient to regrow the amorphous region created by Si ion implantation and to produce good crystalline quality SOS layers. From these regrowth investigations, some alternative processess to produce low-defect-density SOS are proposed.