A capacitive micromachined ultrasonic transducer including a lower electrode, an upper electrode, and a membrane attached to the upper electrode and positioned between the lower electrode and the upper electrode. Anchors are connect to the membrane and the lower electrode such that a cavity is defined between the lower electrode and the membrane. One or more posts are positioned within the cavity, the posts partially buried within the membrane and extending towards the lower electrode. A method of producing a capacitive micromachined ultrasonic transducer includes forming an oxide growth layer on a device layer of undoped silicon and removing portions of the oxide growth layer to form anchors extending beyond the outer surface of the device layer and posts partially buried within post holes in the device layer and extending beyond the outer surface of the device layer.

A semiconductor oxide plate is formed on a recessed surface in a semiconductor matrix material layer. Comb structures are formed in the semiconductor matrix material layer. The comb structures include a pair of inner comb structures spaced apart by a first semiconductor portion. A second semiconductor portion that laterally surrounds the first semiconductor portion is removed selective to the comb structures using an isotropic etch process. The first semiconductor portion is protected from an etchant of the isotropic etch process by the semiconductor oxide plate, the pair of inner comb structures, and a patterned etch mask layer that covers the comb structures. A movable structure for a MEMS device is formed, which includes a combination of the first portion of the semiconductor matrix material layer and the pair of inner comb structures.

A capacitive sensor that includes: a first substrate layer; and a device layer having a movable portion. The movable portion has a first main surface facing the first substrate layer and at least one first protrusion on the first main surface. The first protrusion has a first top portion having a curved surface in a central area of the first protrusion in a plan view of the device layer, and a first slope around the first top portion. The capacitive sensor is configured to detect a change in electrostatic capacity based on a distance between the first substrate layer and the movable portion.

Aspects of this disclosure relate to driving a capacitive micromachined ultrasonic transducer (CMUT) with a pulse train of unipolar pulses. The CMUT may be electrically excited with a pulse train of unipolar pulses such that the CMUT operates in a continuous wave mode. In some embodiments, the CMUT may have a contoured electrode.

A piezoelectric microelectromechanical systems microphone is provided comprising a sensor, an anchor region at which the sensor is supported by a substrate, a first region of the sensor adjacent to the anchor region having a first compliance, the first region having at least one piezoelectric layer and at least one electrode, and a second region of the sensor, the second region being adjacent to the first region, having at least one piezoelectric layer and at least one electrode, and having a second compliance, the first and second compliances being different. A method for manufacturing a piezoelectric microelectromechanical systems microphone is also provided.