Plasma treatment apparatus, a method of monitoring a process of manufacturing a semiconductor device by using the same, and a method of manufacturing a semiconductor device including the monitoring method

A plasma treatment apparatus includes a light generator that generates light, a chamber that receives the light generated from the light generator, an optical element provided between the light generator and the chamber, a light detector that detects the light reflected in the chamber, and a controller connected to the light generator and the light detector. The chamber includes an electrostatic chuck provided in a lower portion of the chamber, an edge ring provided around the electrostatic chuck, an outer wall for sealing an inner space of the chamber, and a gas supply that injects a process gas into the chamber. The optical element branches the generated light to irradiate branched light to different regions of the chamber.