Patent ID: 6904808

Claim:
A pressure sensor characterized by comprising: a pressure sensor chip having a base made of α-phase aluminum oxide, a diaphragm made of α-phase aluminum oxide arranged on a major surface of said base, a capacitive chamber formed from a recess in said base and covered with said diaphragm, a stationary electrode arranged in a bottom portion of said capacitive chamber, and a movable electrode fixed to said diaphragm in said capacitive chamber to oppose said stationary electrode; and a plate member made of α-phase aluminum oxide which is connected to said pressure sensor chip through an intermediate product layer made of α-phase aluminum oxide, wherein said intermediate product layer is formed by heating a solution formed from a solution in which a compound containing aluminum and oxygen is dissolved to change the solution into an intermediate product made of amorphous aluminum oxide or aluminum oxide with a phase other than an α phase, and thereafter causing phase transition of the resultant intermediate aluminum oxide into α-phase aluminum oxide.