A wafer, a fabricating method of the same, and a semiconductor substrate are provided. The wafer includes a first substrate layer formed at a first surface, a second substrate layer formed at a second surface opposite to the first surface, the second substrate layer having a greater oxygen concentration than the first substrate layer, and an oxygen diffusion protecting layer formed between the first substrate layer and the second substrate layer, the oxygen diffusion protecting layer being located closer to the first surface than to the second surface.