Si1-yCy alloy layers deposited on (1 0 0) Si forma tensile-strained layer, similar to strained-Si on a relaxed SiGe buffer. We present the results of fabrication of heterojunction metal oxide semiconductor field effect transistor (MOSFET) devices using Si1-yCy alloy layers, deposited by UHVCVD. By developing a low temperature process flow (<750 degreesC), processing concerns for these types of films are alleviated. We present the results of Si1-yCy/Si heterojunction NMOSFET and PMOSFET devices. For small amounts of C (similar to0.5%), we found significant enhancement for PMOSFET devices; however, NMOSFET devices showed significant degradation. We show that with increasing fields and C concentrations, device performance may be hampered by alloy scattering in spite of the favorable bandstructure. (C) 2003 Elsevier Ltd. All rights reserved.