According to advantages of silicon on nothing（ SON） technology in making high quality monocrystalline silicon pressure sensing diaphragm and vacuum sealed cavity

SON structure is applied in manufacture of capacitive absolute pressure sensor. Theoretical model for sensor pressure detection is established based on shell theory

and theoretical calculation and finite element simulation are performed on pressure sensing diaphragm of sensor and sensitivity of the sensor is analyzed by capacitance change model. Micro-capacitance detecting system based on Pcap01 chip is designed is given. For the pressure sensing diaphragm

whose radius is 100 μm and thickness is 1. 7 μm

the initial capacitance is 0. 278 p F

and the sensitivity of sensor is obtained to be 0. 86 f F/k Pa.