The observation of room temperature sub-60 mV/dec subthreshold slope in MOSFET with ferroelectric layers in the gate stacks has attracted much attention. However, little consideration is given to reliability, which affects the long-term stability of the device. In this work, we investigate the reliability of the oxide layer in the negative capacitance field effect transistor (NCFET) by analyzing the electric field distribution across the oxide layer using Sentaurus Technology Computer-Aided Design (TCAD). Our results show that the electric field strength across the oxide layer (E) of the NCFET is reasonably higher than that of the MOSFET, and the specific E ratio of the NCFET to MOSFET ranges from 1.23 to 1.79. This result can be definitely ascribed to the voltage amplification generated by the NC effect and clearly indicates that the NCFET is more likely to experience dielectric breakdown compared with the MOSFET. Rather than the conventional method for reducing E by lowering the oxide layer thickness, our work provides a new strategy for increasing the thickness of the oxide layer and ferroelectric layer at the same time, thus effectively reducing the off-current and decreasing the E, thereby leading to a lower breakdown risk as well as reduced off-current in the NCFET. Our results definitively stress the efficient modulation effect of the ferroelectric layer toward achieving robust devices and provide brand-new guidance for designing NCFET devices with enhanced reliability.