Abstract: A capacitive pressure sensor has a plate and a diaphragm formed of alumina and hermetically sealed in a spaced relationship, thereby defining a chamber therebetween. Conductive layers are formed on the plate and the diaphragm in opposition. An evacuation passage is formed through the plate such that the chamber pneumatically communicates with the outside. A recess is formed in an outer portion of the evacuation passage, and a tapered throat is formed in an inner portion of the evacuation passage. The chamber is substantially evacuated, and the evacuation passage is hermetically sealed by placing an indium chip and then an alumina plug in the recess. The plug is forced against the indium chip, thereby extruding indium down into the throat and up into the recess around the plug. By extruding the indium, the indium chip is plastically deformed, thereby exposing unoxidized indium to the alumina of the plate and the plug. An oxidation reduction reaction occurs and forms a chemical bond.