Summary: Micro Electro Mechanical Systems has roots dating back to the early days of the IC industry. It is a logical extension of the silicon processes used to fabricate integrated circuits. These processes, which were originally developed to build microelectronic devices, are also capable of building micromechanical devices having structures capable of motion in a microscopic scale. MEMS devices are built in much the same way as a silicon integrated circuit. Various films such as polysilicon, silicon nitride, silicon dioxide, aluminum and gold are deposited and patterned to produce complicated, multilayer three-dimensional structures. However, the major difference is the release step at the end. In a MEMS device, some of the layer materials are removed using a selective etch, leaving a device with moveable elements.