The thermoelectric properties of silicon (Si) thin films prepared by microwave plasma chemical vapour deposition were studied. For preparation, monosilane (SiH4) was used as the source gas, and phosphine (PH3) and diborane (B2H6) were used as the doping gases. X-ray diffraction shows that Si films were polycrystalline and that the average grain size of these films was approximately 100 nm. Measurement of the thermoelectromotive force between Si films and the counter electrodes revealed that the thermoelectric power depends on the flow rate of the doping gas, and that the Si films prepared at the B2H6/SiH4 flow rate of 0.05% showed a maximum thermoelectric power of approximately 0.9 mV K-1.