MEMS designers often use numerical simulation for detecting errors in the mask layout. Numerical simulation involves generating 3D models of MEMS device from the mask layout and process description. The generated models can be meshed and simulated over different domains. This report describes an efficient algorithm that can generate 3D geometric models of MEMS devices. Specifically, the algorithm emulates the manufacturing of a single functional polysilicon layer MEMS devices using the MUMPSprocess.