Comparative Study of Negative Capacitance Ge pFETs With HfZrOxPartially and Fully Covering Gate Region

We report a comparative study of the negative capacitance (NC) Ge pFETs with HfZrOx(HZO) partially and fully covering gate region. Utilizing the layout with HZO partially covering the gate, the internal voltage gain dVint/dVGS> 10 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 CFEproduces the much better capacitance matching between CFEand the MOS capacitance of TaN/HfO2/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.