This paper focuses on implementing a novel thermal switch and variable capacitance design by using commercially available CMOS MEMS process which can approach in a micro electrostatic converter system. In this system, there are two major parts. First is the variable capacitance, and the second is the thermal switch. In the variable capacitance, it implement by UMC 0.18μm one-poly seven-metal (1P7M) CMOS MEMS process. In the post-process, the silicon-oxidation have been released and the gap between two metal layers filled with PDMS (Polydimethylsiloxane). Filling with PDMS is to significantly increase C max.