Photomask and method for forming wiring pattern using the same

A photomask used for exposure to form a resist pattern having nonuniform thickness, said photomask comprising:

• a transparent mask substrate;
• and
• a plurality of square mask cells provided on a planar region on said mask substrate, each of said mask cells having a side shorter than a resolution limit of an optical system of an exposing device in which said photomask is used,
• wherein said mask cell includes at least one of a light transmitting region and a light shielding region formed of a light shielding film provided on said mask substrate;
• wherein a light intensity of a transmitted light of said mask cell is a standardized light intensity, and is determined based on a ratio of an area of said light transmitting region to an area of said mask cell;
• wherein said planar region includes a first region, a second region surrounding said first region, a third region surrounding said second region, and a fourth region outside said third region;
• wherein said first region includes a first group of mask cells transmitting lights of a first light intensity greater than zero and less than or equal to 1;
• wherein said second region includes a second group of mask cells transmitting lights of said first light intensity at a boundary with said first region, transmitting lights of a second light intensity greater than zero and less than said first light intensity at a boundary with said third region, and transmitting lights of light intensities changing from said first light intensity to said second light intensity from said boundary with said first region to said boundary with said third region;
• wherein said third region includes a third group of mask cells transmitting lights of a third light intensity greater than zero and less than said second light intensity, and
• wherein said fourth region includes a fourth group of mask cells transmitting lights of a fourth light intensity greater than or equal to zero and less than said third light intensity.