Deep levels in 3C-SiC on Si grown by chemical vapor deposition using hexamethyldisilane (HMDS) were investigated by the deep level transient spectroscopy (DLTS). 3C-SiC epilayers with various thicknesses were grown by changing the growth time. Relatively thin epilayers (<1 µm) showed DLTS signals in a wide temperature range. This indicates that these epilayers have defects distributed in a wide energy range. These defects seem to originate from the 3C-SiC/Si heterointerface. On the other hand, relatively thick epilayers (>2.2 µm) showed only one DLTS peak, which corresponds to a defect having an activation energy of about 0.25 eV. This defect is a donor defect and is identical with a defect observed in 3C-SiC grown from SiH₄ + C₃H₈.