Abstract: Methods of acquiring a through-focus scanning optical microscopy (TSOM) image and inspecting a semiconductor device are provided. A method of acquiring the TSOM image includes: acquiring a plurality of actual images of different focal positions and out-of-focus degrees (distances) of the actual images with respect to an inspection object through an optical tool; acquiring a plurality of virtual images having different focal positions from the actual images and the focal positions thereof, based on the actual images and the out-of-focus degrees of the actual images; and acquiring a TSOM image of the inspection object by using the actual images and the virtual images. According to a method of acquiring the TSOM image and the method of inspecting the semiconductor device, it is possible to acquire high-precision TSOM images of the object with less effort and time and to inspect the semiconductor device efficiently and at low cost.