Abstract: A method for making a three dimensional structure of the aperture in a photoresist layer on a semiconductor substrate by differentiating dose of exposure light between parts of a photoresist layer. One example of the three dimensional structure is an overhang-platform structure; that is, one side wall of a narrow aperture has an overhang and the opposite side wall has a platform. By separately forming one photoresist layer segment having the overhang wall and the other photoresist layer segment having the platform wall, the distance between the edges of the overhang and the platform can be made smaller than the resolution limit of the photoresist material, which enables making a path line on a substrate whose width is smaller than the resolution limit. Many types of photoresist layers and photomasks for producing such photoresist layers are disclosed.