Comparative Study of Negative Capacitance Ge pFETs With HfZrOx Partially and Fully Covering Gate Region
We report a comparative study of the negative capacitance (NC) Ge pFETs with HfZrO<sub><italic>x</italic></sub> (HZO) partially and fully covering gate region. Utilizing the layout with HZO partially covering the gate, the internal voltage gain <italic>dV</italic><inline-formula> <tex-math notation="LaTeX">$_{{\textsf {int}}}$ </tex-math></inline-formula>/<italic>dV</italic><inline-formula> <tex-math notation="LaTeX">$_{{\textsf {GS}}} > \textsf {10}$ </tex-math></inline-formula> is demonstrated in NC Ge pFETs, which is attributed to the NC effect induced by HZO film. NC transistor demonstrates the hysteresis above 2 V, the sub-60 mV/decade subthreshold swing, and the improved drive current over internal-gated MOSFET. As the area of HZO is increased to fully cover the gate, the increased ferroelectric capacitance <inline-formula> <tex-math notation="LaTeX">${C} _{{\textsf {FE}}}$ </tex-math></inline-formula> produces the much better capacitance matching between <inline-formula> <tex-math notation="LaTeX">${C} _{\textsf {FE}}$ </tex-math></inline-formula> and the MOS capacitance of TaN/HfO<sub>2</sub>/Ge channel, contributing to the elimination of hysteresis of the NC Ge pFET. NC Ge pFETs with the gate fully covered by HZO achieve a much higher gate capacitance peak and a 36% enhancement in drive current compared to the devices with HZO partially covering gate.