The most appropriate method to evaluate the process damage is proposed. FeRAM process is used as a damage source. The degradation of the drain current of long-channel MOSFET is larger than that of short-channel MOSFET, although long-channel MOSFET has been believed to be more robust. In the case of short-channel MOSFET, the drain current is limited by saturation velocity, and thus the mobility degradation caused by the process damage has a smaller influence. On the contrary, in the case of long-channel MOSFET, the drain current is not limited by saturation velocity, which leads to the degradation of the drain current owing to the mobility reduction caused by the process damage of the FeRAM capacitor process. These results suggest that the most accurate method for evaluating the process damage is to monitor the degradation of the drain current of long-channel MOSFET.