Micro-electromechanical system (MEMS) techniques, as advanced manufacturing techniques, arise from 1990s, and are widely used to improve the standard and quality of life and enhance national strength. MEMS techniques feature a strong interdisciplinary characteristic. Recently, silicon-based processes already become main processes to manufacture MEMS devices. Nevertheless, due to the complexity to manufacture MEMS, difficulties in integration of MEMS with semiconductor processes have become a limit to MEMS development.
Semiconductor processes have advantages like low cost, high accuracy and consistency. By integrating MEMS processes with semiconductor processes, not only above mentioned advantages can be taken, but also defects of semiconductor devices formed in semiconductor processes may be overcome. Take the gate of a MOS transistor as an example, a conventional gate includes a gate dielectric layer and a gate electrode layer formed on the gate dielectric layer. More information of the gate may be referred to Chinese patent publication No. 1522463. Usually, the gate dielectric layer includes silicon dioxide and the gate electrode layer includes a conducting material such as polysilicon or metal. However, leakage current is likely to occur due to change of interfacial bonding state between the gate dielectric layer and the gate electrode layer, which may affect the normal operation of a transistor.