Microwave heating was utilized for the first time for solid phase crystallization of amorphous silicon films. Microwave heating lowered annealing temperature and reduced the annealing time for complete crystallization. For example, the amorphous silicon film deposited at 400 °C was fully crystallized in 3 h at 550 °C below which glass is available as a substrate. On microwave heating, the hydrogen in the amorphous films diffused out very quickly, but there was no change in structural disorder following hydrogen evolution. The lower temperature crystallization of a-Si films compared to conventional furnace annealing is due to the interaction between microwave and silicon atoms. The grain size of the crystallized silicon films was in the range of 0.55 to 0.78 μm, depending on the deposition temperature. These grain sizes are not so small comparing those of Si films by conventional furnace heating, while the crystallization processing time is much shorter.