Properties of tantalum silicide (TaSix) films deposited from a TaSixcomposite target are studied. Ta‐rich (Si/Ta atom ratio,x=1.83) and Si‐rich (x=2.60) films are deposited by dc magnetron sputtering on Si substrates. In Ta‐rich films, a silicidation reaction occurs with annealing above 700 °C. As a result, Si composition,x, and silicide film thickness increases with consuming Si substrate. Stress changes abruptly from tensile to compressive with this reaction. This stress change leads to peeling in the Ta‐rich film during the silicidation reaction. In Si‐rich films, excess Si precipitates at the interface at 750 °C. However, the stress changes more gently in the Si‐rich film and a more uniform TaSi2/Si interface is formed. Therefore, peeling can be avoided in Si‐rich films.