Ultrahigh density (>10(12) cm(-2)) Fe3Si nanodots (NDs) are epitaxially grown on Si(111) substrates by codeposition of Fe and Si on the ultrathin SiO2 films with ultrahigh density nanovoids. We used two kinds of methods for epitaxial growth: molecular beam epitaxy (MBE) and solid phase epitaxy. For MBE, low temperature (<300 degrees C) growth of the Fe3Si NDs is needed to suppress the interdiffusion between Fe atoms deposited on the surfaces and Si atoms in the substrate. These epitaxial NDs exhibited the ferromagnetism at low temperatures, which were expected in terms of the application to the magnetic memory device materials. (C) 2011 Elsevier B. V. All rights reserved.