This paper describes how faulty thin-film transistors (TFTs) having fragile structures in themselves can be characterized by cross-sectional transmission electron microscopy (X-TEM) through the achievement of pinpoint accuracy in focused ion beam (FIB) etching. We demonstrate X-TEM analysis for faulty TFTs caused by mechanical damages, microvoid in their multilayers and long aluminum whiskers growing from the electrodes. X-TEM specimen were prepared by FIB etching without losing unique structures owing to fragile locations. Cross-sectional bright-field TEM micrographs clearly showed the details of cross sectional structure of fragile location. This pin-point X-TEM is quite helpful to identify faults and to reveal root causes of failures.