The design and simulation of a novel resonant cavity optical modulator incorporating a hybrid silicon/electro-optic polymer slot waveguide structure is presented in this work. The device utilizes the electro-optic polymer in the cavity region to provide an active material for modulation and includes distributed Bragg reflectors in single mode silicon waveguide regions at each end of the cavity to create a narrow response peak at the resonant wavelength. Simulation results show that this electro-optic modulator design can simultaneously attain a large modulation depth, short device length and a low drive voltage, all of which are expected to be necessary for future high speed integrated optics devices. The high operating frequency and complex nature of the structure lead to a need for full 3D simulations in order to obtain accurate propagation characteristics, particularly concerning scattering losses. However, 3D simulations are very computationally expensive, especially during design optimization. Therefore, the periodicity of the device has been exploited to allow a cascade matrix approach to be employed to reduce the necessary computational resources required for accurate simulation of the propagation characteristics. The design and fabrication process have been chosen to allow for the majority of the fabrication to be completed before the electro-optic polymer is introduced into the process, which enables the use of well-established CMOS processing techniques, and should accelerate the transition to hybrid silicon/electro-optic polymer devices in future integrated optics applications.