A wide dynamic range silicon diaphragm vacuum sensor by an electrostatic servo system and an electrical circuit for servo control have been made. In nonservo mode, i.e., when the sensor was used as a capacitive vacuum sensor, a linear characteristic between pressure and output voltage was obtained in the pressure range from 0.1 to 100 Pa. On the other hand, the square root of the servo voltage was proportional to the pressure in a wide pressure range from 0.1 to 530 Pa in servo mode. The servo mechanism is effective for widening the dynamic range of vacuum sensors.