Electrical Characterization of a Second-gate in a Silicon-on-Insulator Transistor

applications in analog and digital circuitry. This study investigates the ability of the JFET bottom-gate to adjust and control several parameters in the FlexfetTM as well as shield against performance degradation due to substrate biasing. The device parameters under investigation include drive current, leakage current, and threshold voltage. The newly assigned F-factor describes the ability of FlexfetTM’s bottomgate to adjust the threshold voltage. FlexfetTM exhibits nearly a 10x and 3.5x increase in drive current for the nMOS and pMOS devices, respectively, with a 1 V bottom-gate voltage swing. Comparing the nominal devices with the low-power devices, both the nMOS and pMOS unexpectedly demonstrated higher leakage current for the low-power biasing. F-factors of 0.53 V/V and 0.38 V/V were calculated for the nMOS and pMOS devices, respectively. With a 40 V swing on the substrate potential, the nMOS device showed less than 12 pA increase in leakage current and no more than 20 mV of unwanted Vt shift. The pMOS measured less than 2 pA increase in leakage current and 10 mV of Vt shift for the same substrate biases.