(Ta₂O₅)_1-x-(TiO₂)_x (TTO) thin films, with x = 0.035, were deposited onto the P/boron-silicon (100) semiconducting substrates by reactive direct current (DC) magnetron sputtering of mosaic Ta and Ti metal targets, at ambient temperature. As-deposited films have been passed through the process of annealing at the temperatures, ranging from 500 to 800 °C. X-ray diffraction measurements, generally, show the formation of Ta₂O₅ structure of the annealed films. Metal–oxide–semiconductor (MOS) structure of Ag/(Ta₂O₅)_1-x-(TiO₂)_x/p-Si (Ag/TTO/p-Si), with x = 0.035, was formed, and capacitance of the structure was measured, at room temperature and 1 MHz. Capacitance of prepared MOS structure was measured, and found generally, increasing with annealing temperature. Among the prepared films, maximum value of dielectric constant was found 45, at 1 MHz, for the films annealed at 700 °C. Frequency dependent behaviour of dielectric loss was observed, and was found minimum value of 0.022, at 200 kHz, for the films deposited at room temperature.