Fluid pressure detector using a diaphragm

A good quality passive-state film is formed on a gas-contact face of a diaphragm of a pressure detector using a sensor chip to prevent corrosion on, or water content emission from, or catalytic action at a gas-contact face, thereby improving production quality in a semiconductor manufacturing process and providing high accuracy pressure detection. The passive-state film is formed on the gas-contact face of the diaphragm when the diaphragm is mounted on a diaphragm base. The diaphragm base is then fixedly secured to a sensor base in which a sensor chip is housed and a pressure transmitting medium is sealed in a gap between the sensor base and the diaphragm base.