Si atomic layer-by-layer epitaxial growth without substrate heating has been investigated using alternate exposure of Si(1 0 0) to SiH4 and to Ar plasma. With an Ar plasma generated by electron cyclotron resonance (ECR) at the Ar pressure of 2.1 Pa (the measured peak energy and the incident density of the Ar ion are about 3 eV and 3 x 10(15) cm(-2) s(-1), respectively), the average deposited Si thickness per cycle increases and saturates with exposure times to SiH4 and to Ar plasma and also with the SiH4 partial pressure. The thickness becomes smaller for the longer interruption of SiH4 introduction until the Ar plasma exposure. In the Si atomic layer-by-layer epitaxial growth processes, their characteristics are qualitatively described in a modified Langmuir-type equation, assuming that the SiH4 coverage is determined by the equilibrium of adsorption/desorption processes of a SiH4 molecule on a single site, and the site density is the same as the surface atom density of Si(1 0 0). (C) 2003 Elsevier Science B.V. All rights reserved.