LONDON — Researchers from Nanoelectronic Devices Laboratory of the Swiss Federal Institute of Technology Lausanne, Switzerland (nanolab.epfl.ch)are set to report on progress on two fundamental energy-efficient devices at the 2008 IEEE International Electron Devices Meeting (IEDM), due to run in San Francisco, Dec. 15 to 17.

The first contribution concerns an active microelectromechanical (MEMS) resonator based on a vibrating-body field effect transistor (VB-FET). This is a hybrid device that exploits the modulation of channel charge and piezoresistivity in the body of an active FET integrated on a resonant MEM structure.

The VB-FET is implemented as a n-channel silicon resonator, on a silicon-on-insulator (SOI) substrate, which is more appropriate for the fabrication of a suspended-body transistor and for a lateral device with vertical isolation. The VB-FET always uses a combination modulation of the output: the FET channel charge modulation that is dominant at the micrometer scale, and the piezoresitivity modulation that is comparable or larger than charge modulation in smaller devices.

The EPFL VB-FET vibrates laterally rather than vertically. Like most MEMS structures the fabricated VB-FET is of micrometer scale with gaps of the order of 150-nm between the vibrating body and the lateral fixed gates.

According to EPFL, VB-FETs with double-gate and four-gate VB-FETs with resonance frequencies of 2MHz and 71MHz, respectively, exhibit built-in amplification, ultra low motional resistances and frequency tuning DC bias. This active MEMS resonator concept, with built-in amplification can achieve a negative resistance of -30 ohms, enabling the possibility of building an oscillator without any sustaining amplifier, thus reducing the power consumption and oscillator size.

The paper also demonstrates a VB-FET mixer-filter based on a single-device operating at 9.84-MHz and a VB-FET oscillator at 2.6-MHz. The VB-FET device is expected to contribute to the miniaturization and the reduction of power consumption in oscillators, mixers and filters for communications circuits.