MEMS switch

1. A MEMS switch comprising:

fixed support;

a plate-shaped flexible beam extending along a first direction having at least one end immovably supported by the fixed support and having an extending movable surface;

a movable electric contact disposed on the movable surface of the flexible beam;

a fixed electric contact disposed above the movable electric contact, facing the movable electric contact and disposed at a fixed position relative to the fixed support;

first piezoelectric driver disposed above the movable surface of the flexible beam, extending along the first direction from a portion above the fixed support towards the movable electric contact, and capable of displacing the movable electric contact towards the fixed electric contact by voltage driving; and

second piezoelectric driver disposed at least on the movable surface of the flexible beam in a region containing the movable contact and extending along the first direction, capable of so driving a movable part of the flexible beam by voltage driving that the movable electric contact is separated from the fixed electric contact;

wherein either of the first piezoelectric driver and the second piezoelectric driver has a lower electrode, a piezoelectric material layer disposed on the lower electrode, and an upper electrode disposed on the piezoelectric material layer,

wherein the movable electric contact is disposed in an intermediate-width region of the flexible beam and the second piezoelectric driver includes a pair of piezoelectric actuators disposed on both outer-width sides of the movable electric contact, and

wherein the fixed support comprises an SOI substrate in which an active Si layer is bonded to an Si support substrate via a silicon oxide layer, and

the flexible beam comprises part of the active Si layer and has a stripe shape having a constant width and extending in a longitudinal direction.

2. A MEMS switch according to claim 1 , wherein the flexible beam has a both-ends supported beam structure and the movable electric contact and the second piezoelectric driver are disposed in an intermediate region between two ends of the both-ends supported beam.

3. A MEMS switch according to claim 1 , wherein the flexible beam has a cantilever beam structure and the movable electric contact and second piezoelectric driver are disposed in vicinity of free end of the cantilever beam.

4. A MEMS switch according to claim 1 , further comprising:

a first control circuit that controls the first piezoelectric driver; and

a second control circuit that controls the second piezoelectric driver.

5. A MEMS switch according to claim 4 , wherein the first control circuit and the second control circuit are coupled through mutual induction.

6. A MEMS switch according to claim 4 , further comprising a microprocessor that controls the first control circuit and the second control circuit.

7. A MEMS switch according to claim 6 , further comprising a counter that counts number of operations of the first control circuit and the microprocessor activates the second control circuit once in response to a plural times of activation of the first control circuit.