Patent ID: 8283253

Claim:
A pattern forming method for forming a pattern of a predetermined shape which serves as a mask for etching an etching target layer on a substrate, the method comprising: a first pattern forming process for forming a first pattern on the etching target layer by patterning a first mask material layer made of a photoresist; a trimming process for reducing a width of the first pattern to a predetermined width; a boundary layer forming process for forming a boundary layer, which is made of a material selectively removable with respect to the photoresist, on top portions and sidewall portions of the first pattern and an exposed surface of the etching target layer; a second mask material layer forming process for forming a second mask material layer, which is made of a material selectively removable with respect to the boundary layer, on a surface of the boundary layer; a second mask material removing process for removing a part of the second mask material layer to expose top portions of the boundary layer; a second boundary layer forming process for forming a second boundary layer, which is made of a material selectively removable with respect to the photoresist, on the second mask material layer and the boundary layer; a third mask material layer forming process for forming a third mask material layer, which is made of a photoresist and formed in a predetermined pattern, on the second boundary layer; an etching process for etching the second boundary layer into the predetermined pattern by using the third mask material layer as a mask and etching the second mask material layer by using the second boundary layer of the predetermined pattern as a mask; and a boundary layer etching process for exposing the first pattern and forming a second pattern having the second mask material layer on the boundary layer by etching the boundary layer.