A method and apparatus for testing semiconductors comprising shallow trench isolation (STI) edge structures. An edge intensive shallow trench isolation structure (500) is coupled to a voltage source (310) and a current profile is recorded. A planar structure (600) on the same wafer is coupled to a voltage source and a current profile is recorded. A comparison of current profiles obtained for the two types of structures may indicate the presence and/or extent of STI corner effects. More specifically, a steeper slope for a normalized current versus time plot for an STI edge intensive structure (500) compared to a slope of a normalized plot of a planar structure (600) is indicative of an increased rate of electron trapping in STI corners, which may indicate that the STI corners are too thin. In this novel manner, STI corner thickness is observed in a non-destructive, electrical test process, resulting in higher quality and greater reliability of semiconductors using STI processes.