Atom probe tomography (APT) is a novel characterization technique capable of resolving the three-dimensional atomic distribution in materials or devices, achieving sub-nanometer spatial resolution and nearly 20 ppm compositional detection limit. This unique combined analytical capability sets it apart from transmission electron microscopy (TEM), which is limited by compositional limit, and secondary ion mass spectrometry, which is limited by spatial resolution. Hence, it has become a crucial characterization technique for contemporary research and development in miniaturized, heterogeneous, and three-dimensional semiconductor devices.