Cross Field-Effect Transistor With Adjustable Threshold Voltage and High Ring-Oscillator Frequency

This study introduces a cross field-effect transistor (CrossFET) design, which features two orthogonally crossed transistors: an n-channel field-effect transistor (NFET) and a p-channel field-effect transistor (PFET). The CrossFET can function in three modes: pure NFET, pure PFET, and inverter, depending on the applied bias conditions. When operating purely as either an NFET or a PFET, the threshold voltage ( ${V} _{\text {t}}$ ) of the CrossFET can be precisely modulated by applying a specific voltage to the source and drain of the complementary transistor in the CrossFET. In the inverter mode, the NFET and PFET constitute an inverter. The simulation results indicate that the frequency of the CrossFET-based ring oscillator is 20% higher than that of the gate-all-around (GAA) FET-based counterpart for the same gate length because of the shared channel. The fabrication process of the CrossFET is compatible with that of GAA FETs. Both GAA FETs and CrossFETs can be implemented on the same wafer.