Several silicon‐on‐insulator guided‐wave structures have been analyzed as potential electro‐optic waveguide modulators using thepisces‐iitwo‐dimensional (2D) device simulation program. From the electron and hole concentration data, the 2D refractive index profile is obtained. The profile is then spatially averaged with respect to a 2D cosine representation of the guided‐waveEfield to obtain the effective modal index changes at 1.3 and 1.55 &mgr;m. The channel‐waveguide devices studied include the metal‐oxide‐semiconductor (MOS) diode, and the one or two‐gate metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with single‐or double‐transverse injection. The single‐gate double‐injection MOSFET modulator offers the most promise with 10−3refractive index changes possible, changes comparable in size to the Pockels effect in LiNbO3or GaAs.