Free-carrier electro-optic modulators are important active devices in Photonic Integrated Circuits (PICs) because of the feasibility of modulating the phase and power of input light signals. By applying external fields, carrier density around PN junction is changed and induces the change of the refractive index, resulting in the delay of propagation phase or decay of power. However, free carriers change not only the refractive index, but also temperature. For a forward-biasing operation, a huge amount of current will induce a high temperature distribution due to a self-heating effect, which compensates the changes of index. In this video, a full 3D EO modulator was designed and simulated in Synopsys Sentaurus TCAD Workbench with Device and BeamPROP BPM. The index compensation from self-heating effects in this modulator was simulated to show the seamless interface between two foundry-verified simulators in the multi-physics domain.