Annealing of an amorphized Si layer formed by As+ implantation into an SOI (silicon-on-insulator) Si layer was performed. Arsenic ions are implanted at 100 keV and 5.0 x 10(15) ions/cm(2) into thin (56 nm thick) and thick (1.5 mu m thick) Si layers. Rutherford backscattering spectrometry and transmission electron microscope measurements show the formation of a 130 nm thick amorphous layer by this implantation. In the thick Si layer, recrystallization occurred at the amorphous/crystalline interface with an annealing at 850 degrees C. However, no recrystallization occurred within the thin Si layer because a crystalline interface did not exist. Thus, a high resistivity, amorphous n-Si layer with low electron mobility was formed.