We have investigated the growth of microcrystalline silicon films by electron cyclotron resonance plasma chemical vapor deposition (ECR-PCVD) using He as the ECR gas at substrate temperatures in the range of 180 to 550 degrees C with He to silane ratios (He/SiH4) of 1: 4, and 9. With ratios of 4 and 9, the volume fractions of microcrystalline silicon increase with temperature and exceed 90% at 550 degrees C. To study the role of He plasma; we prepared silicon films using a layer-by-layer technique and found that long exposure to He plasma changes the structure of amorphous silicon to microcrystalline.