A new acoustoelectric phase shifter is proposed which produces a direct phase shift of a SAW on piezoelectric substrate. Computations of the attenuation and phase lag versus resistivity due to a silicon wafer air‐gap coupled toyz‐LiNbO3are presented. The use of the variation of the resistivity of the silicon to control the phase of a SAW was demonstrated using the photogeneration of carriers and the field‐effect control of the surface resistivity. A 180° shift was obtained with a +30‐V transverse voltage pulse.