Reflective mask blank, reflective mask and method of manufacturing the same, and method of manufacturing semiconductor device

A reflective mask comprising:

• a substrate;
• a multilayer reflective film provided on the substrate;
• and
• an absorber film provided on the multilayer reflective film and having a patterned absorber pattern,
• wherein the absorber film comprises:
• a high absorption coefficient element selected from the group consisting of cobalt (Co) and nickel (Ni), and
• an element that increases a dry etching rate, and
• wherein a lower surface region of the absorber film includes a surface of the absorber film that faces the substrate and an upper surface region of the absorber film includes a surface of the absorber film that faces away from the substrate, and
• wherein a concentration (atomic %) of the high absorption coefficient element in the upper surface region is higher than a concentration (atomic %) of the high absorption coefficient element in the lower surface region, and
• wherein the absorber film optionally includes both of Co and Ni,
• wherein the concentration of the high absorption coefficient element decreases monotonically from the upper surface region to the lower surface region in a depth direction of the absorber film, and
• wherein a concentration of the element that increases the dry etching rate increases monotonically from the upper surface region to the lower surface region in the depth direction of the absorber film.