High quality ultra-thin silicon-on-insulator (SOI) materials have been fabricated by low-energy low-dose separation-by-implantation-of-oxygen (SIMOX) method. The thicknesses of the top silicon and the buried oxide (BOX) layers are only 70 and 40 nm, respectively, for the sample implanted with dose of 1.8 x 10(17) O+/cm(2) at the ion energy of 45 keV. The pinhole density of the BOX layer is less than 0.1 cm(-2), and the thickness uniformity of both the top silicon and the BOX layers over the whole wafer is within 2 nm. The fabricated high quality ultra-thin SOI materials are desirable for the advanced integrated circuits (ICs) manufacturing. (C) 2002 Elsevier Science B.V. All rights reserved.