Two testing methods are used simultaneously to analyze the retention time of deep trench DRAM. Both the gate and base voltages were modulated to find proper testing conditions for the failure analysis. Proper testing conditions will provide useful messages to minimize the abnormal range required for failure analysis, which therefore helps to catch exactly the addresses with leakage and the leakage mechanisms of them. Next, the exact failed addresses can be transferred to the production line to carry out laser repairing and ultimately the product yield is possibly to be improved. Therefore, the objective of this paper is to emphasize the importance of proper parameter setting for the failure testing of deep trench DRAM, which is greatly connected to the through put of products.