In this work, a leaky-Ferroelectric Field Effect Transistor (FeFET) neuron is introduced as a physical reservoir in a reservoir computing scheme. Compared to a conventional FeFET reservoir control sample, which did not show leaky behavior, the proposed leaky-FeFET neuron-based physical reservoir exhibited 78.6% and 62.9% improvements in memory capacity for Short Term Memory (STM) and Parity Check (PC) tasks, respectively. The improvements are attributed to the temporal memory effect induced by the leaky-integrating neuronal behavior, which originates from the retention degradation of the FeFET.