Here, a new design based on the optimization of the fabrication parameters and the introduction of a bossed plate as the sensing element will be illustrated.All three sensors proposed open up new possibilities for pressure measurements and have the scope to offer a solution for very sensitive pressure measurements, pressure monitoring in harsh environment or pressure monitoring inside the human inhibitor licensed body.2.?Capacitive Pressure Sensors in Silicon TechnologyCapacitive sensing has been historically a mechanical engineering field, mainly concerning positioning, pressure and sounds measurements [1]. In the beginning of the 70��s Heerens [2] reviewed various techniques to mechanically design capacitive sensors; in the same years Jones and Richards [3] described an ultra sensitive capacitive micrometer and in 1982 Hugill [4] presented a capacitive displacement transducer.

These Inhibitors,Modulators,Libraries sensors usually employed a transformer ratio bridge circuit in order to achieve the maximum possible sensitivity and a high degree of immunity to parasitic capacitance. Transformer ratio bridges, together with charge Inhibitors,Modulators,Libraries transfer circuits and more complicated methods such as switched capacitor circuits are still Inhibitors,Modulators,Libraries used to interface capacitive transducers [5�C7]. While signal conditioning methods has always relayed on analog or mixed-signals electronics, the capacitive senor design, due to the needs of miniaturization, power consumption and costs issues, has shifted from being realized by bulk mechanical parts to microfabricated silicon dies. An early example of this device was fabricated for medical purposes by Frobenius et al.

[8] in 1973. In 1986 Ko [9] compares the capacitive pressure sensor with the well established piezoresistive device. In many respects capacitive sensing results more promising than its counterpart. In 1993, Puers [10], is of the same opinion as Ko and identifies pressure as the main field of application for capacitive measurements. Inhibitors,Modulators,Libraries In 1997, Baxter [11] wrote a book which threat thoroughly the wast subject of capacitive sensing but, with respect to silicon technology, he refers to Drug_discovery the article written by Puers four years earlier. At the same time Eaton and Smith [12] reviewed the state of the art in micromachined pressure sensor technology, in their opinion capacitive micromachined pressure sensors were still under development.

Only this century saw the first commercialized devices as pointed out by Gao and Zhang [13] in 2004. Some example are the tire pressure monitoring (TPM) sensor developed by Motorola, VTI absolute pressure sensor for implantable medical devices and reference 2 Vaisala barometric sensor. Finally, in 2007, Wise [14] predicts a future were MEMS of different type will be part of wireless integrated microsystems that will serve as the front-ends of information networks used in a huge variety of contexts; the capacitive pressure sensor is seen as one of the most probable candidate to be integrated in these systems.2.1.