A pressure sensor is manufactured by joining two wafers, the first wafer comprising CMOS circuitry and the second being an SOI wafer. A recess is formed in the top material layer of the first wafer, which is covered by the silicon layer of the second wafer to form a cavity. Part or all of the substrate of the second wafer is removed to forming a membrane from the silicon layer. Alternatively, the cavity can be formed in the second wafer. The second wafer is electrically connected to the circuitry on the first wafer. This design allows to use standard CMOS processes for integrating circuitry on the first wafer.