Nancy, If you oxide is good, you will end up having trapped charge, it's a matter of time and quantity. The way to avoid it is to supply some leakage mechanism -i.e. high value resistor in series. shay -----Original Message----- From: Jia, Nancy Subject: [mems-talk] RE: Charge effects in electrostatic actuators This is based on a typical MEMS Surface Micromachining Process. It is like a parallel capacitor with a fixed polysilicon electrode at the bottom of the device and a movable doped polysilicon membrane on the top that is grounded. There is a thermal oxide or nitride deposited on the fixed polysilicon to prevent electrical shorting between the two electrodes. Hope this give you enough details to answer my original questions.