Patent ID: 6870937

Claim:
An electroacoustic transducer comprising: a lower electrode comprising a semiconductor substrate; an upper electrode, at least partially supported by the semiconductor substrate of the lower electrode, the upper electrode including an oscillation portion and a support portion for supporting the oscillation portion at least at a part of a periphery of the oscillation portion, wherein said oscillation portion of the upper electrode oscillates upon receiving an acoustical signal sufficiently so as to change a distance between the upper and lower electrodes thereby changing a capacitance of a capacitor formed thereby so that an electrical signal indicative of the acoustical signal is generated; and an insulating layer for insulating the lower electrode from the upper electrode, wherein the upper electrode has an up and down portion(s) in the oscillation portion and/or in the support portion to provide a cavity which is located directly between the upper electrode and the semiconductor substrate of the lower electrode, and wherein the cavity is in air communication with atmosphere/air exterior the transducer so that air can move therebetween, and wherein the lower electrode completely seals off a lower side of the cavity.