Epitaxial growth of Si1-x-yGexCy epitaxial films on Si(100) has been investigated at 550 degrees C in a SiH4-GeH4-CN3SiH3-H-2 gas mixture using an ultraclean hot-wall low pressure chemical vapor deposition (LPCVD) system. With increasing CH3SiH3 partial pressure, the deposition rate decreases depending on the Ge fraction, the C concentration increases linearly up to about 10(21) cm(-3), and the Ge fraction increases at a high CH3SiH3 partial pressure. These characteristics can be explained by the modified Langmuir-type formulation with the assumption that CH3SiH3 is adsorbed more preferably at the Si-Ge pair site, suppressing SiH4 and GeH4 adsorption. The electrical characteristics of the P-implanted Si1-x-yGexCy epitaxial film were evaluated and it was found that electrically inactive P increases at a C concentration over 3 X 10(20) cm(-3), which corresponds to the concentration where the lattice constant deviates from that calculated using Vegard's law.