The Rashba spin-orbit interaction in InGaAs quantum wells (QW) is studied using the weak antilocalization analysis as a function of the structural inversion asymmetry (SIA). A clear cross-over from positive to negative magnetoresistance near zero-magnetic field is observed by controlling the degree of the SIA in the QWs. This is a strong evidence of a zero-field spin splitting that is induced by the Rashba effect. The spin interference effect in a gate controlled mesoscopic loop structure is studied in the presence of the Rashba spin-orbit interaction. The oscillatory behaviors as a function of the gate voltage can be attributed to the spin interference effect. This result shows that the spin precession can be controlled by the gate voltage.