The fabrication of a 20 nm strained-Si on a 360 nm relaxed-SiGe layer structure using SIMOX technology was successfully demonstrated for the first time. The thin relaxed-SiGe layer on SiO2 was obtained by the direct implantation of oxygen into the thick SiGe layer, and by annealing. It was found that hydrogen termination produced by HF treatment allows successful regrowth of strained-Si layer on the thin relaxed-SiGe layer by ultra-high vacuum chemical vapor deposition (UHV-CVD). Structure analyses such as secondary ion mass spectroscopy (SIMS), Rutherford back-scattering spectroscopy (RBS) analysis, and cross-sectional transmitting electron microscopic (TEM) revealed the perfection of the layer structure of Si/SiGe/SiO2. The fully strained-Si on the relaxed-SiGe layers was also confirmed by Raman spectroscopy. It was revealed that the combination of the SIMOX process and the regrowth on the SiGe layer provides an advanced layer structure including this strained-Si for future novel devices.