We report on the electric field dependence of ferroelectric phase transition in epitaxial SrTiO3 (STO) thin films grown by the pulsed-laser ablation deposition method. Metallic oxides SrRuO3 (SRO) and La0.5Sr0.5CoO3 (LSCO) were used as the bottom electrodes, and the bottom electrodes influence the dielectric properties of STO films. The change in the dielectric properties originates from the different work functions and the lattice mismatches among STO film, the bottom electrode, and the substrate. However, the field-induced ferroelectric phase transition temperatures of the STO/SRO/(100) STO and the STO/LSCO/(100) LaAlO3 systems are proportional to the applied electric field, indicating a field-induced first-order ferroelectric phase transition. © 2000 American Institute of Physics.