Abstract: A method of testing a semiconductor structure such as a finished or part-finished semiconductor wafer, a die on such a wafer, part of such a die, or even one functional element (e.g. a transistor or memory cell) of such a die. The method includes the steps of charging at least a part of the semiconductor structure; applying an electric field perpendicular to a surface of the structure while charging so as to determine charging potential and polarity (i.e. charging either positively or negatively); interrogating the structure including the charged part with a charged particle beam, such as an electron beam, so as to obtain voltage contrast data for the structure; and analyzing the data to determine the functionality of the element.