In the below 20nm semiconductor era, all the device structure parameters should be carefully controlled; the film thickness needs to be controlled by below 0.1 Å level, the tolerance of the line width is less than 1nm, and the devices need to be free of nano-particles. In order to achieve these requirements, we must know the status of processes exactly. Therefore the metrology and inspection equipment employs the cutting edge technologies in the vast fields, such as optics, electron optics, surface physics, mechanics, data mining, image processing, computational simulation, and so on. In this presentation, it is reviewed how we use the fundamental physics in the semiconductor metrology and inspection industry.