The effects of the residual stress (either compressive or tensile) induced during the heat-treatment process on the electrical properties of Pb(Zr0.52Ti0.48)O-3 (PZT) films were investigated. The PZT films were deposited on platinized silicon substrates by the rf-magnetron sputtering method using a single oxide target. After their deposition, the films were bent elastically by means of a specially designed fixture during the annealing process. Residual stress was induced in the film by removing the substrate from the fixture after annealing. The ferroelectric and piezoelectric properties of the films were markedly changed by the residual stresses; the remnant polarization (P-r) and saturation polarization (P-sat) increased when a compressive stress was induced. On the other hand, the piezoelectric properties increased when a tensile stress was induced in the film.