Some interesting phenomena relating to dislocation behavior occurring near the seed/grown -crystal interface during the growth of heavily B-doped Si crystals have been observed, which have not been reported in the literature. The generation and/or propagation of dislocations have been shown to be suppressed- remarkably due to an impurity hardening effect in heavily B-doped or heavily B- and Ge-codoped Si crystals. As a result, in the heavily B-doped or Band Ge-codoped Si crystals, dislocations did not multiply in spite of the fact that some dislocations could not always be fully eliminated even after use of a severe thin neck process. Consequently, neckless growth of a dislocation-free Si crystal has been successfully achieved, based on this discovery. Furthermore, a new kind of so-called "robust Si wafer" has been proposed, which exhibits a high resistance to thermal stress and is suitable for any kind of epitaxial growth without the generation of misfit dislocations. (c) 2004 Published by Elsevier B.V.