Method of operating scanning electron microscope (sem) and method of manufacturing semiconductor device using the same

A method of manufacturing a semiconductor device, the method comprising:

• forming a mold including a plurality of insulating layers that are alternately stacked with a plurality of sacrificial layers on a wafer and a plurality of channel structures passing through the mold in a vertical direction;
• forming a word line cut vertically passing through the mold to expose the plurality of sacrificial layers;
• removing the sacrificial layers and forming gate electrodes between the insulating layers, wherein each of the gate electrodes that underlies at least one of the gate electrodes horizontally protrudes from an overlying gate electrode of the gate electrodes;
• forming contact holes exposing top surfaces of the gate electrodes;
• and
• measuring the contact holes,
• wherein the measuring of the contact holes includes
• setting a first energy as blocking energy of a first energy filter and setting a second energy as blocking energy of a second energy filter,
• irradiating an input electron beam onto the wafer and sensing emission electrons emitted from the wafer in response to the input electron beam being irradiated onto the wafer to generate a first image and a second image, wherein the first image is generated based on a first portion of the emission electrons having energy greater than or equal to the first energy, wherein the second image is generated based on a second portion of the emission electrons having energy greater than or equal to the second energy, and the first energy is less than the second energy, and
• performing a differential operation on the first image and the second image to generate a differential image.