A capacitive micromachined ultrasound transducer (cMUT) and fabrication method of the same are provided. The cMUT has a substrate, a curved membrane disposed on top of the substrate, and a flexible membrane disposed on top of the curved membrane. The curved membrane has a raised portion which is higher than a recessed portion relative to the substrate, and is supported by a support standing on a major surface of the substrate. The flexible membrane includes a first region mounted to the raised portion of the curved membrane, and a second region extending over the recessed portion of the curved member. Methods for fabricating the cMUT are also disclosed.