A method for forming an interconnection structure, comprising: forming a first dielectric layer pattern over a substrate covering the first dielectric layer pattern with metal and planarizing the metal to expose an upper surface of the first dielectric layer pattern and form a first metal layer pattern; forming a second dielectric layer pattern over the first dielectric layer pattern and the first metal layer pattern; covering the second dielectric layer pattern with metal and planarizing the metal to expose an upper surface of the second dielectric layer pattern and form a second metal layer pattern, wherein the second dielectric layer pattern comprises a portion overlying a first portion of the first metal layer pattern, and the second metal layer pattern comprises a first portion overlying a second portion of the first metal layer pattern, and a second portion overlying a portion of the first dielectric layer pattern; forming a mask pattern of a mask material over the second dielectric layer pattern and the second metal layer pattern, wherein the mask pattern comprises a first sub-pattern of mask features overlying said first portion of the first metal layer pattern, a second sub-pattern of mask features overlying said first portion of the second metal layer pattern, and a third sub-pattern of mask features overlying said second portion of the second metal layer pattern; and in an etching process comprising using the mask pattern as an etch mask, transferring: the first sub-pattern into said first portion of the first metal layer pattern to form a set of lower metal features, the second sub-pattern into said first portion of the second metal layer pattern and said second portion of the first metal layer pattern to form a set of stacked metal features, and the third sub-pattern into said second portion of the second metal layer pattern to form a set of upper metal features. forming a first dielectric layer pattern over a substrate covering the first dielectric layer pattern with metal and planarizing the metal to expose an upper surface of the first dielectric layer pattern and form a first metal layer pattern; forming a second dielectric layer pattern over the first dielectric layer pattern and the first metal layer pattern; covering the second dielectric layer pattern with metal and planarizing the metal to expose an upper surface of the second dielectric layer pattern and form a second metal layer pattern, wherein the second dielectric layer pattern comprises a portion overlying a first portion of the first metal layer pattern, and the second metal layer pattern comprises a first portion overlying a second portion of the first metal layer pattern, and a second portion overlying a portion of the first dielectric layer pattern; forming a mask pattern of a mask material over the second dielectric layer pattern and the second metal layer pattern, wherein the mask pattern comprises a first sub-pattern of mask features overlying said first portion of the first metal layer pattern, a second sub-pattern of mask features overlying said first portion of the second metal layer pattern, and a third sub-pattern of mask features overlying said second portion of the second metal layer pattern; and in an etching process comprising using the mask pattern as an etch mask, transferring: the first sub-pattern into said first portion of the first metal layer pattern to form a set of lower metal features, the second sub-pattern into said first portion of the second metal layer pattern and said second portion of the first metal layer pattern to form a set of stacked metal features, and the third sub-pattern into said second portion of the second metal layer pattern to form a set of upper metal features.