The crystallization process of chemically vapor deposited (CVD) amorphous Si films was studied by using a differential scanning calorimeter. A sharp exothermic peak due to amorphous–polycrystalline transition was obtained in the 665–700 °C range. The crystallization temperature was determined to be 665 °C. Transmission-electron diffraction and transmission-electron microscopic examinations revealed that, when amorphous Si film is heated at a slightly higher temperature than the crystallization temperature, the Si dendrite grains nucleate, and grow in size with heating time.