We observed concentric ring patterns on a Ta film deposited on Si(100) after thermal treatments of annealing at 900 degrees C for 24 h, followed by flashing at 1300 degrees C for a few seconds in an ultrahigh vacuum. The diameters of the ring pattern range from a few tens of micrometers to several hundred micrometers. Atomic force microscopy studies indicate a height of about 100 nm for the rings. Auger electron spectroscopy analyses show that the TaSi2 layer is formed on the Si surface during heating and that the silicide layer is about four times thicker than the as-deposited Ta film.