A high quality epitaxial Si layer by molecular beam epitaxy (MBE) on Si (001) substrates was demonstrated to fabricate a channel with low density defects for high-performance FinFET technology.In order to study the effects of fin width and crystallography orientation on the MBE behavior,a 30 nm thick Si layer was deposited on the top of an etched Si fin with different widths from 10 nm to 50 nm and orientations of and .The result shows that a defect-free Si film was obtained on the fin by MBE,since the etching damage was confined in the bottom of the epitaxial layer.In addition,the vertical growth of the epitaxial Si layer was observed on sub-10 nm Si fins,and this was explained by a kinetic mechanism.