Low-loss silica-based single-mode waveguides are fabricated on Si substrates by flame hydrolysis deposition and reactive ion etching. The waveguide loaded with a thin film heater operates as a phase shifter due to the refractive index dependence on temperature. The phase shifter can afford optical switching and/or tuning functions for silica-based integrated-optic devices. The waveguides have large stress-induced birefringence due to the difference in thermal expansion coefficients between SiO2 and Si. Waveguide birefringence control techniques are proposed for constructing various polarization insensitive and sensitive devices.