Phase shift mask blank and phase shift mask

A phase shift mask blank, which is an original plate of a phase shift mask exposed to an ArF excimer laser light, wherein:

• the phase shift mask blank has a light transmissive substrate, a phase shift film and a light-shielding film;
• the phase shift film is provided between the light transmissive substrate and the light-shielding film;
• the phase shift amount of the phase shift film with respect to the ArF excimer laser light is 160° to 180°
• the transmittance of the phase shift film is 2 to 40%;
• the light-shielding film consist of a plurality of layers;
• the optical density of the entire light-shielding film is 1.8 to 2.6;
• the ratio of the optical density of a layer A constituting the plurality of layers to the sum of the optical densities of all the layers other than the layer A is 1:5 to 1:19;
• each of the layers constituting the light-shielding film contains a metal;
• and
• the layers other than the layer A consist of a film comprising:
• the same metal as that contained in the layer A;
• N;
• and O, and the sum of the content of N and the content of O is 40 to 65 atomic %.