Power consumption is one of the most challenging bottlenecks for complementary metal‐oxide–semiconductor integration. Negative‐capacitance field‐effect transistors (NC‐FETs) offer a promising platform to break the thermionic limit defined by the Boltzmann tyranny and architect energy‐efficient devices. However, it is a great challenge to achieving ultralow‐subthreshold‐swing (SS) (10 mV dec−1) and small‐hysteresis NC‐FETs simultaneously at room temperature, which has only been reported using the hafnium zirconium oxide system. Here, based on a ferroelectric LiNbO3 thin film with great spontaneous polarization, an ultralow‐SS NC‐FET with small hysteresis is designed. The LiNbO3 NC‐FET platform exhibits a record‐low SS of 4.97 mV dec−1 with great repeatability due to the superior capacitance matching characteristic as evidenced by the negative differential resistance phenomenon. By modulating the structure and operating parameters (such as channel length (Lch), drain–sourse bias (Vds), and gate bias (Vg)) of devices, an optimized SS from ≈40 to ≈10 mV dec−1 and hysteresis from ≈900 to ≈60 mV are achieved simultaneously. The results provide a new potential method for future highly integrated electronic and optical integrated energy‐efficient devices.

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