In this paper, a two-dimensional analytical model for the tunnel field effect transistor (TFET) on the silicon-on-insulator substrate is proposed. The accurate electrostatic potential and electric field of the device are obtained by solving the Poisson equation with appropriate boundary conditions. The accuracy of the proposed analytical model is verified by comparing with numerical simulation. It is shown that the electrical behavior of the TFET is more properly described by defining the zero vertical electric field at the channel/buried oxide interface. Furthermore, this analytical model is extended to implement in the hetero-material-gate (HMG) TFET. The physical principle of the HMG TFET can also be depicted, and electrical properties are characterized using this model.