We have developed a novel technique to deposit poly-Si films on insulating substrates in an electron cyclotron resonance (ECR) SiH4/H-2 plasma-enhanced chemical vapor deposition (PECVD) and investigated the effect of reactive species on polycrystalline silicon (poly-Si) film formation at low substrate temperatures. The charged species incident on the substrate were successfully shut out by using permanent magnets set above the substrate in an ECR SiH4/H-2 plasma. As a result, the films formed without charged species were found to have better crystallinity than those formed with charged species at a low substrate temperature of 150 degrees C. From results of the atomic force microscope, it was found that the surfaces of films formed without charged species were smoother than those of films formed with charged species at a substrate temperature of 300 degrees C. Therefore, it was clarified that the charged species deteriorated the crystallinity and the surface roughness while the neutral reactive species played an important role for improving them in the poly-Si film formation at low temperatures using the ECR SiH4/H-2 PECVD method.