A thermoelectric thin-film device consisting of n-type Bi₂Te₃ and p-type Sb₂Te₃ thin-film legs was prepared on a glass substrate by using co-evaporation and annealing process. The Seebeck coefficient and the power factor of the co-evaporated Bi₂Te₃ film were −30 µV/K and 0.7 × 10⁻⁴ W/K²·m, respectively, and became substantially improved to −160 µV/K and 16 × 10⁻⁴ W/K²·m by annealing at 400°C for 20 min. While the Seebeck coefficient of the co-evaporated Sb₂Te₃ thin film was 72 µV/K, it increased significantly to 165–142 µV/K by annealing at 200–400°C for 20 min. A maximum power factor of 25 × 10⁻⁴ W/K²·m was achieved for the co-evaporated Sb₂Te₃ film by annealing at 400°C for 20 min. A thermopile sensor consisting of 10 pairs of n-type Bi₂Te₃ and p-type Sb₂Te₃ thin-film legs exhibited a sensitivity of 2.7 mV/K.