The Vibrating Body Transistor

This paper presents a hybrid resonator architecture called the vibrating body field-effect transistor (VB-FET), which combines a silicon microelectromechanical (MEM) resonator and a FET in a single device. The active device provides improved motion sensing at the mechanical resonance based on charge-and/or piezoresistive-drain-current modulations. We detail the principles of the VB-FET for a clamped-clamped-beam resonator design. The different transduction mechanisms occurring in this structure are discussed, and the benefit of the FET detection with respect to the capacitive transduction in terms of reduced motional resistance is highlighted. The experimental characteristics of the resulting devices are detailed, including a full scattering-parameter characterization and temperature characterizations. An increase in the signal transmission by more than +30 dB over the conventional capacitive transduction is demonstrated under equivalent biasing conditions at 2 MHz. Intrinsic signal amplification in a hybrid MEM resonator is another unique property of active resonators demonstrated in this paper for VB-FET resonators.