We studied the dependence of selective epitaxially grown silicon (SEG-Si) morphology under ultrahigh vacuum chemical vapor deposition (UHV-CVD) conditions by using a mixture of disilane (Si2H6) and chlorine (Cl-2) gases on Si(100) substrates patterned a metal oxide semiconductor transistor with Si3N4 sidewalls. We confirmed that the morphology of the SEG-Si is strongly dependent on the dry etching conditions used for formation of the sidewall structures and that the Cl-2 plasma etching process results in lower damage to the substrate surface than CHF3/Ar plasma etching. It was demonstrated that by combining low-damage sidewall etching with Cl-2 plasma and the UHV-CVD process with deoxidation effects it was possible to flatten the SEG-Si surface at temperatures below 700degreesC without the need for preheating at a higher temperature. (C) 2004 Elsevier B.V. All rights reserved.