MEMS based sensors, particularly capacitive sensors, potentially can address critical considerations for users including accuracy, repeatability, long-term stability, ease of calibration, resistance to chemical and physical contaminants, size, packaging, and cost effectiveness. Accordingly, it would be beneficial to exploit MEMS processes that allow for manufacturability and integration of resonator elements into cavities within the MEMS sensor that are at low pressure allowing high quality factor resonators and absolute pressure sensors to be implemented. Embodiments of the invention provide capacitive sensors and MEMS elements that can be implemented directly above silicon CMOS electronics.

A resonator includes a vibration portion with upper and lower electrodes with a piezoelectric film disposed therebetween. Moreover, a protective film is provided to face the piezoelectric film with the upper electrode interposed therebetween and is exposed in a first region in the vibration portion. A conductive film is provided to face the piezoelectric film with the protective film interposed therebetween and is exposed in a second region that is adjacent to the first region in the vibration portion. A connection electrode is formed in the protective film to electrically connect the conductive film to the lower electrode. The upper electrode is formed such that an area of a region overlapping the conductive film is equal to or smaller than half of a total area of the conductive film and/or avoids the region overlapping the conductive film.

Reference oscillators are ubiquitous in timing applications generally, and in modern wireless communication devices particularly. Microelectromechanical system (MEMS) resonators are of particular interest due to their small size and potential for integration with other MEMS devices and electrical circuits on the same chip. In order to support their use in high volume low cost applications it would be beneficial for MEMS designers to have MEMS resonator designs and manufacturing processes that whilst employing low cost low resolution semiconductor processing yield improved resonator performance thereby reducing the requirements of the oscillator circuitry. It would be further beneficial for the oscillator circuitry to be able to leverage the improved noise performance of differential TIAs without sacrificing power consumption.

A resonator includes a vibration portion with upper and lower electrodes with a piezoelectric film disposed therebetween. Moreover, a protective film is provided to face the piezoelectric film with the upper electrode interposed therebetween and is exposed in a first region in the vibration portion. A conductive film is provided to face the piezoelectric film with the protective film interposed therebetween and is exposed in a second region that is adjacent to the first region in the vibration portion. A connection electrode is formed in the protective film to electrically connect the conductive film to the lower electrode. The upper electrode is formed such that an area of a region overlapping the conductive film is equal to or smaller than half of a total area of the conductive film and/or avoids the region overlapping the conductive film.

A MEMS resonator is provided with improved electrical characteristics and reduced spurious resonances. The MEMS resonator includes two or more first rectangular resonator plates with lengths greater than their respective widths. Moreover, the MEMS resonator includes two or more second rectangular resonator plates that are positioned parallel to the first resonator plates in the widthwise direction of the MEMS resonator. The length of the second resonator plates is different than the length of the first resonator plates to reduce spurious resonances.

A calibration system is provided for an oven controlled MEMS oscillator. The calibration system includes control circuitry that to separately selects predetermined target set-point values and controls a heater inside the oven controlled MEMS oscillator based on each of the selected target set-point values to adjust a set-point of the oven controlled MEMS oscillator. The system further includes an oscillation measurement circuit that measures respective oscillation frequencies at each adjusted set-point corresponding to each of the selected predetermined target set-point values. The measured oscillation frequencies can then be used to determine a target set-point operation value for the oven controlled MEMS oscillator, which can be sued to calibrate the oven controlled MEMS oscillator.

In a quartz crystal unit, the unit comprising a quartz crystal resonator having a base portion, and first and second tuning fork arms connected to the base portion, the base portion having a length less than 0.5 mm and greater than a spaced-apart distance between the first and second tuning fork arms, each of the first and second tuning fork arms having a width less than 0.1 mm and a length less than 1.56 mm, and a plurality of different widths including a first width and a second width greater than the first width, at least one groove being formed in at least one of opposite main surfaces of each of the first and second tuning fork arms so that a length of the at least one groove is within a range of 0.3 mm to 0.79 mm, the quartz crystal resonator being housed in a case, and a lid being connected to the case.

A mechanical resonator includes two identical plates, and a decoupling structure comprising at least two first connectors, each first connector connecting the decoupling structure to a respective one of the two identical plates, and an anchor disposed at a center of the decoupling structure. Each of the two identical plates may be a square plate adapted to resonate in Lam?-mode. Further, each of the two identical plates may comprise a plurality of square plates, each square plate disposed next to one another. The decoupling structure further comprises a first ring connected to each of the two identical plates via a respective one of the at least two first connectors. The decoupling structure may further comprise a second ring connected to an inside of the first ring via at least two second connectors, wherein the anchor is disposed at a center of the second ring.

A vibration device that includes a support member, vibration arms connected to the support member and each having an n-type Si layer which is a degenerate semiconductor, and electrodes provided so as to excite the vibration arms, and silicon oxide films containing impurities in contact with a respective lower surface of the n-type Si layers of each vibration arm.

A MEMS resonator is provided with a high quality factor and lower motional impedance. The MEMS resonator includes a silicon layer having opposing surfaces, a piezoelectric layer above one of the surfaces of the silicon layer, and a pair of electrodes disposed on opposing surfaces of the piezoelectric layer, respectively. Moreover, the piezoelectric layer has a crystallographic axis that extends at an angle relative to the vertical axis of the MEMS resonator.