Formation of semiconductor calcium silicide Ca2Si on Si(111)7x7 and 2/3 root 3-Mg surface phases and bulk Mg2Si film was studied. Conditions of high quality Ca2Si film growth were found. Formation of Ca surface phase was demonstrated at the initial stage of Ca2Si film growth on 2/3 root 3-Mg surface phase at narrow temperature range. Band gap of this surface phase and 2/3 root 3-Mg were obtained. (C) 2010 Published by Elsevier B.V.