Current trends in the semiconductor and electronics industry require memory devices to be made smaller, faster and require less power consumption. In addition to active circuitry on such integrated circuit devices, micro-electromechanical (MEMS) devices are sometimes employed in various applications. One exemplary application involves aircraft or vehicle applications, where a MEMS device is employed to detect a change in acceleration. In early systems, the active circuitry was manufactured separately from the MEMS device, however, in recent years attempts have been made to integrate the MEMS device and the active circuitry on the same semiconductor substrate, and thus reside in the same package.
Prior art MEMS acceleration sensors consist in some instances of a cantilever type beam extending over an underlying layer with a gap therebetween. As the acceleration of a body associated with the sensor changes, the cantilever bends with respect to the underlying layer, causing a change in the gap distance. By employing the cantilever as one element of a capacitor, the change in gap distance results in a change of capacitance, thereby reflecting the change in acceleration.
Prior art MEMS acceleration sensor systems were not space efficient. That is, the large MEMS portion of the device was fabricated next to the active circuitry employed to detect and communicate the change in capacitance. For example, as illustrated in prior art FIG. 1, an integrated circuit die 10 has a MEMS structure 12 formed next to active circuitry 14, and the MEMS structure 12 occupies a modest amount of die area. This lateral juxtaposition of the MEMS sensor and the active circuitry disadvantageously increases the die size, thereby causing such integrated circuit chips to be rather expensive. Therefore improvements in MEMS sensor devices are desired.