Multilayer substrate

Patent Pending PROBLEM TO BE SOLVED: To provide a multilayer substrate capable of correctly measuring temperatures during a step of crystal-growing an oxide thin film on a translucent substrate and a step of thermal processing. ; SOLUTION: In the multilayer substrate, a multilayer film 10 is formed on a main surface opposite to a main surface A of the translucent substrate 1 on which the oxide thin film is laminated. In the multilayer film 10, a dielectric film 2, an Au (gold) film 3, and an oxide film 4 are sequentially laminated from the translucent substrate 1 side.