Ultra low pressure sensor

A sensor for acoustic applications such as a silicone microphone is provided containing a backplate provided with apertures and a flexible diaphragm formed from a silicon on insulator (SOI) wafer which includes a layer of heavily doped silicon, a layer of silicon and an intermediate oxide layer that is connected to, and insulated from the backplate. The arrangement of the diaphragm in relation to the rest of the sensor and the sensor location, being mounted over the aperture in a PCB, reduces the acoustic signal pathway which allows the sensor to be both thinner and more importantly, enables there to be a greater back volume.