(An) abrupt switching phenomenon of metal-oxide-semiconductor field-effect transistor by gate charging

Abstract

According to the scaling down of the MOSFET, the high power consumption, which is caused by the high operating voltage and leakage current, have emerged as one of the most problematic part of the silicon-based CMOS. In order to reduce both the operating voltage and the leakage current, the subthreshold swing (SS) of the transistor must be reduced. However, the SS of MOSFET cannot be reduced to less than 60 mV/dec at room temperature because its operating mechanism is based on the thermal diffusion. As a result, various steep-slope devices with the SS lower than 60 mV/dec had been proposed, but those steep-slope devices have low on-current (ION) or limitation on scalability. Therefore, new steep-slope device with high on-current (ION) and scalability is necessary. In this research, an abrupt switching phenomenon of MOSFET by gate charging is proposed. The reason of the technical limit in the existing steep-slope devices, is the change on the MOSFET structure and the operating principle. Therefore, in the proposed FET (called “Γ-FET”), the MOSFET structure is used as it is, and the steep-slope operation is provided by changing the gate operation. The Γ-FET has a structure in which the transition layer and the triggering gate are mounted on the gate of the conventional MOSFET. Since the MOSFET structure is maintained, the high on-current and the scalability are achieved in Γ-FET. The steep-slope of the Γ-FET is based on the internal gate structure and transition between triggering gate and internal gate. In the Γ-FET, the transition current amplify the small change of the triggering gate voltage to abrupt change of the internal gate voltage at the subthreshold region of bottom MOSFET. The steep-slope characteristic of Γ-FET is observed in the fabricated device, and the steep-slope mechanism is analytically modeled and verified by simulation.