The lithium insertion and extraction reaction characteristics in Fe/Si multilayer thin-film anodes have been investigated. As determined from the features of the differential capacity curves, the structural changes in Si phase, associated with the crystalline Li15Si4 phase formation, are affected by the thickness of the Si layer in Fe/ Si multilayer film and the deposition condition like surface roughness of substrate. For Fe/Si multilayer film with a 130-angstrom-thick Si layer, a crystalline Li15Si4 phase has not been formed during cycling. As the Si layer thickness to 2000 angstrom, crystallization also becomes evident. However, when the multilayer film is deposited on a rough surface induced by chemical etching, the formation of the Li15Si4 phase appears to be suppressed. This is attributed to the distinct interfacial feature in the film deposited on a rough surface, showing significantly interdiffused interfaces between Fe and Si layers. (c) 2006 The Electrochemical Society.