The problem of nonlinear coupling of surface waves in an insulating piezoelectric to an adjacent but mechanically isolated semiconductor is treated theoretically. A perturbation approach is used with a small‐signal nonlinear field expansion to obtain nonlinear coupling equations in terms of the linear material parameters and geometry of the system. The limiting case of the linear solution is related to other linear coupling theories. The special case of the surface‐wave convolver is treated and compared to other convolver theories.