Exposure method based on multiple exposure process

A multiple exposure method using plural masks, said method comprising:

• exposing a position where an image of a low-contrast pattern is to be formed on the basis of a mask, of the plural masks, having fine lines extending in different directions, with an image of a pattern of a mask having a phase difference of 180 degrees between adjacent patterns, whereby a contrast of an exposure amount distribution related to the pattern of the low contrast is increased;
• and
• placing boundaries of the phase shift mask so that regions divided by the boundaries have substantially the same area or angle.

A multiple exposure method using plural masks, said method comprising:

• exposing a position where an image of a low-contrast pattern is to be formed on the basis of a mask, of the plural masks, having fine lines extending in different directions, with an image of a pattern of a mask having a phase difference of 180 degrees between adjacent patterns, whereby a contrast of an exposure amount distribution related to the pattern of the low contrast is increased;
• and
• placing boundaries of the phase shift mask to divide a region having a larger area or angle.

A multiple exposure method, comprising:

• a first exposure step for exposing a first pattern which includes fine lines extending in different directions, wherein the fine lines or extensions of them intersect with each other;
• and
• a second exposure step for exposing a second pattern having a phase difference between adjacent patterns, wherein the phase difference between the adjacent patterns defines the boundaries of an even number.