The electrical characteristics of W-Si(100) Schottky barrier junctions formed by sputter deposition of W on both n- and p-type Si(100) have been measured in the temperature range 95-295 K using current-voltage and capacitance-voltage techniques. Auger electron and Rutherford backscattering spectroscopies were used to characterize the Si(100) surface prior to metal deposition, and to monitor the reaction between W and Si upon annealing. The results showed that initial silicide formation has very little or no effect on the barrier height. Annealing after initial silicide formation caused the junction characteristics to strongly deviate from the ideal thermionic emission behavior. For junctions with ideal thermionic emission behavior the barrier height was found to decrease with increasing temperature with a coefficient consistent with the predictions of recent models of barrier formation based on Fermi-level pinning in the center of the semiconductor indirect band gap.