US Patent 7191661 Capacitive pressure sensor

A capacitive pressure sensor made up of two silicon on insulator (SOI) wafers lying opposite of each other and joined to each other in a vacuum-tight manner, a recess being formed between the two wafers. The first wafer exclusively supports the evaluation circuits required for measuring the applied pressure and a capacitive electrode, and the second wafer has a recess formed by surface micromechanics processes, in which the counter electrode to the capacitive electrode of the first wafer is situated. The second wafer at the same time forms a cover for the first wafer.