Mach-Zehnder (MZ) lanthanum-modified lead-zirconate-titanate (PLZT) electro-optic modulators were fabricated on a silicon substrate by aerosol deposition. The fabricated modulator has a reversed-ridge-waveguide structure (with a 1.8-µm-wide ridge) and electrodes for applying a voltage perpendicular to the PLZT core layer. The modulator also has an MZ interferometer structure in which the device length and the electrode length of phase shifter are 1.5mm and 500µm, respectively. Optical-characteristics measurements showed that the 2-GHz optical output signal was produced by the modulator. The optical performance proves the validity of using the modulators on silicon substrates for on-chip optical interconnects.