Polycrystalline &bgr;-SiC, with grain size up to 1500 Å, has been room-temperature-deposited on Si substrates by electron cyclotron resonance chemical vapor deposition. Microwave power and the hydrogen carrier gas are the key parameters to lower the deposition temperature. According to the results of the cross-sectional transmission electron microscopy, the grain size appeared to be in the same scale as that deposited at 500 °C while a large amount of plasma-induced defects were observed in the Si substrate for the room-temperature-deposited samples. Hence, aCH4-plasma treatment prior to the &bgr;-SiC film growth was adopted, forming a SiC-like interfacial layer to suppress the substrate damages. ©1997 American Institute of Physics.