Mask blank, transfer mask, and methods of manufacturing the same

A mask blank, comprising:

• a transparent substrate having a main surface;
• and
• a thin film for forming a transfer pattern on the main surface of the transparent substrate;
• wherein the thin film is made of a material containing a transition metal and silicon and further containing at least one of oxygen and nitrogen,
• wherein the thin film has as a surface layer an oxide layer having an oxygen content higher than an oxygen content of the thin film of a region excluding the surface layer,
• wherein the thin film is formed so that a thickness of an outer peripheral portion is greater than a thickness of a central portion on a side of the main surface, and
• wherein the oxide layer is formed so that a thickness of the outer peripheral portion is greater than a thickness of the central portion on the side of the main surface.