A pressure sensor apparatus is disclosed herein, which generally includes a sensor element, a flexible sensor diaphragm in intimate contact with the sensor element at all pressure levels and temperatures, and a package base and a package cover for hermetically sealing the sensor element and the flexible sensor diaphragm within a hermetically sealed sensor package to provide pressure sensor data thereof. The sensor element can be implemented as a quartz sense element to produce a SAW pressures sensor. The pressure sensor apparatus can be alternatively based on other sensing technologies, such as silicon piezoresistive, ceramic capacitive and others.