This work presents a failure analysis study on domestic operational amplifiers, revealing that the main cause of device failure is the short circuit of stacked MIS capacitors induced by process changes. Under low electric fields, the capacitors perform normally, but under high electric fields, Fowler-Nordheim tunneling and defect accumulation caused by hot electron collisions ultimately lead to capacitor short circuits. Using Sentaurus TCAD simulations, we verified the impact of doping atom concentration differences at the interface on the oxide layer growth rate and proposed process improvement recommendations to enhance the reliability of domestic chips.