Polycrystalline silicon is grown at a temperature of 300 degrees C by microwave-excited plasma enhanced chemical vapor deposition using SiH4/Xe. The grain size measured by x-ray diffraction is about 25 nm. High-density (> 10(12) cm(-3)) plasma having very low electron temperature (<1 eV) is excited by microwave irradiation using radial line slot antenna. We present the implementation of this system for the growth of poly-Si. Low-energy (3 eV), high-flux ion bombardment utilizing xenon ion on a growing film surface activates the film surface and successfully enhances surface reaction/migration of silicon, resulting in high quality film formation at low temperatures.