A method for forming an interconnect structure, comprising the steps of: a. Providing a first entity comprising: i. a first set of one or more line structures having a top surface, comprising: - a first set of one or more conductive lines, - a first set of one or more dielectric lines of width (w) made of a first dielectric material, aligned with and overlaying said first set of one or more conductive lines, and comprising said top surface, ii. a second dielectric material of such a nature that said first dielectric material can be etched selectively with respect to said second dielectric material, said second dielectric material surrounding each line structure and having a top surface coplanar with the top surface of said one or more line structures; b. Providing a patterned mask on said first entity, wherein the pattern comprises: i. at least one via exposing the whole width (w) of an underlying dielectric line of said first set of one or more dielectric lines, and/or ii. at least one trench exposing the whole width (w) of at least one dielectric line of said first set of one or more dielectric lines; and c. Etching selectively said first dielectric material with respect to said second dielectric material through said patterned mask so as to form one or more vias in said first dielectric material, thereby exposing a portion of said set of one or more conductive lines, d. Removing said patterned mask, thereby uncovering a perforated surface; wherein said first set of line structures provided in step a have the first dielectric material exposed at the top surface thereof and have side surfaces (24, 25) comprising a conductive portion and a dielectric portion wherein at least said conductive portion is at least partially coated with a first dielectric barrier material, said first dielectric barrier material being such that said first dielectric material can be etched selectively with respect to said first dielectric barrier material. a. Providing a first entity comprising: i. a first set of one or more line structures having a top surface, comprising: - a first set of one or more conductive lines, - a first set of one or more dielectric lines of width (w) made of a first dielectric material, aligned with and overlaying said first set of one or more conductive lines, and comprising said top surface, ii. a second dielectric material of such a nature that said first dielectric material can be etched selectively with respect to said second dielectric material, said second dielectric material surrounding each line structure and having a top surface coplanar with the top surface of said one or more line structures; i. a first set of one or more line structures having a top surface, comprising: - a first set of one or more conductive lines, - a first set of one or more dielectric lines of width (w) made of a first dielectric material, aligned with and overlaying said first set of one or more conductive lines, and comprising said top surface, - a first set of one or more conductive lines, - a first set of one or more dielectric lines of width (w) made of a first dielectric material, aligned with and overlaying said first set of one or more conductive lines, and comprising said top surface, ii. a second dielectric material of such a nature that said first dielectric material can be etched selectively with respect to said second dielectric material, said second dielectric material surrounding each line structure and having a top surface coplanar with the top surface of said one or more line structures; b. Providing a patterned mask on said first entity, wherein the pattern comprises: i. at least one via exposing the whole width (w) of an underlying dielectric line of said first set of one or more dielectric lines, and/or ii. at least one trench exposing the whole width (w) of at least one dielectric line of said first set of one or more dielectric lines; and i. at least one via exposing the whole width (w) of an underlying dielectric line of said first set of one or more dielectric lines, and/or ii. at least one trench exposing the whole width (w) of at least one dielectric line of said first set of one or more dielectric lines; and c. Etching selectively said first dielectric material with respect to said second dielectric material through said patterned mask so as to form one or more vias in said first dielectric material, thereby exposing a portion of said set of one or more conductive lines, d. Removing said patterned mask, thereby uncovering a perforated surface;