Current VLSI devices have very complicated circuit designs and very small feature size. As a result, fault isolation on failing devices becomes a more and more challenging task. Although backside photoemission technique is commonly used to detect the failure site covered with multiple metal layers, it has the disadvantages of more time consumption and less success rate. Without a localized failure site, it will be very difficult, sometime even impossible, to find the physical evidence for the failures. This article describes a method that has been successfully used for isolating the wordline leakage on a memory FLASH device using FIB cutting and passive voltage contrast on the leaky wordline. The concept of this article is not just limited to this application; rather it can be used for all similar types of fault isolation work for other applications.