W delta doping in Si epitaxial growth by WF6 and SiH4 reaction has been investigated using an ultraclean cold-wall low-pressure chemical vapor deposition (CVD) system. Atomic-layer order W deposition is performed on wet-cleaned Si(1 0 0) substrate at 100 degreesC using WF6 and SiH4. Si epitaxial growth is achieved by SiH4 reaction at 480 degreesC on 4 x 10(13) cm(-2) W deposited Si(1 0 0), however, it is found that almost all the deposited W atoms segregate on the deposited Si film. It is also found that such segregation is suppressed by the atomic-order W diffusion into Si(1 0 0) substrate by the heat treatment at 520 degreesC before the Si deposition. In the case of the Si film deposited on the 1.3 x 10(14) cm(-2) W diffused Si, the reflection high-energy electron diffraction (RHEED) pattern indicates the crystallinity and the roughness degrade. In the case of the Si film deposited on the 5 x 10(13) cm(-2) W diffused Si, the RHEED pattern shows streaks with Kikuchi lines. As a result, the W delta doping in the Si epitaxial growth is achieved, in which the W concentration is as high as 6 x 10(21) cm(-3) and the incorporated W atoms is confined within 2 nm-thick region. (C) 2003 Elsevier Science B.V. All rights reserved.