Method of manufacturing mask and method of manufacturing display device

A method of manufacturing a display device, the method comprising:

• preparing a mask assembly;
• arranging the mask assembly to face a substrate, the substrate extending in a first direction;
• attaching the mask assembly to the substrate;
• and
• supplying, by a deposition source, a deposition material to pass through the mask assembly to deposit the deposition material on the substrate,
• wherein the mask assembly includes:
• a mask frame;
• and
• a mask sheet including a plurality of openings and having edges bonded to the mask frame,
• a first portion of the mask sheet located between two adjacent openings includes a first surface, a second surface, and a lateral surface, the first surface facing the mask frame, the second surface being opposite to the first surface, and the lateral surface connecting the first surface to the second surface,
• wherein the mask sheet further includes:
• a second portion protruding in a second direction from the first portion, wherein the second direction is perpendicular to the first direction and is opposite direction of the direction toward the mask frame from the first portion;
• and
• a first angle between the lateral surface and the second surface is less than a second angle at which the deposition material is incident with respect to the substrate,
• wherein a surface of the second portion is closer to the substrate than the second surface of the first portion, and
• wherein a width of the surface of the second portion is less than a width of the second surface of the first portion.