Micro-electro-mechanical system device

A micro-electro-mechanical system (MEMS) device, comprising:

• a substrate having a center and four sides;
• a proof mass suspended over the substrate, the proof mass including at least one proof mass body and a proof mass frame connected to and surrounding the proof mass body, the proof mass body being located within the proof mass frame, and the proof mass frame including at least one self-test frame which is located at an outer side of the proof mass body, whereby the proof mass body is closer to the center of the substrate than the self-test frame is;
• and
• at least one self-test electrode inside the self-test frame, and connected to the substrate;
• wherein the at least one self-test electrode and the self-test frame are configured to receive a voltage difference in between for checking an offset of the proof mass or a flexibility of the structure of the MEMS device and when the voltage difference is applied between the self-test electrode and the self-test frame, the proof mass is driven to have an in-plane movement, and wherein a capacitance signal between the self-test electrode and the self-test frame is not used for calculating the in-plane movement of the proof mass.