A phase shift mask includes a substrate including first and second transmissive regions alternately disposed, and absorbers disposed on a surface of the substrate such that each absorber is sandwiched between the first and second transmissive regions. A phase shifter is defined by a difference between a surface height of the first transmissive region and a surface height of the second transmissive region. At least the first transmissive region among the first and second transmissive regions has a trench. An aperture portion formed between opposite side walls of respective adjacent absorbers has a width that increases along a depth direction of the substrate. Each trench has a width that increases along the depth direction of the substrate.