In order to integrate various photonic functions and/or many channels into one chip, (Pb,La)(Zr,Ti)O3 (PLZT) waveguide technologies have been developed. PLZT is one of the best candidates in terms of dense integration and device miniaturization due to its efficient voltage-induced index change and high refractive index. We have established a solid-phase epitaxy to grow low-loss PLZT thin film waveguides, since the formation of low optical propagation loss PLZT waveguides had been difficult with typical vapor phase growth techniques. PLZT waveguides with PLZT buffer layers are grown on Nb-doped semiconductive SrTiO3 substrates for the effective overlap integral of the optical field and the electric field. Efficient control of light coupled in the waveguides is achieved by applying voltage between the top electrodes and the substrates to induce the excellent electro-optic properties of PLZT waveguides. In addition, optical switching devices, which are the key elements of various integrated devices, are fabricated in the PLZT waveguides, showing low-voltage drive and ultra-fast response characteristics. Further key developments such as matrix switches, switch-VOA arrays, and modulator arrays directed toward integrated photonics are also discussed.