Novel structures for carrier‐induced electro‐optical phase modulation in crystalline silicon are examined. A new dual‐injection field‐effect transistor structure for guided‐wave light modulation at 1.3 &mgr;m is proposed and analyzed. It consists of an elongated cathode‐anode‐gate structure integrated in a rib waveguide. Dual‐gate and single‐gate control are considered. The overlap between the plasma charge density and the optical guided mode is computed. For a cathode‐anode voltage of 0.32 V, the effective refractive index of the waveguide mode changes by &Dgr;N=1×10−3when the gate voltage is altered by 12 V. Numerical estimates of the bias current, pinchoff voltage, interaction length, and modulator speed are given.