A method for forming horizontal nanowires, the method comprising: - providing a substrate comprising a dielectric layer and a fin structure comprising a protruding portion protruding from the dielectric layer, the protruding portion comprising a multi-layer stack consisting of a layer of a first material stacked alternately and repeatedly with a layer of a second material, the bottom layer of the multilayer stack being a layer of the first material, - masking a part of the protruding portion including the top and the sidewalls thereof by providing a dielectric layer (1, 10) thereby creating an un-masked portion of the protruding portion, and - sequentially forming horizontal nanowires (11, 12, 13) starting from the top of the un-masked portion, wherein the forming is done by repeatedly performing a cycle comprising: - removing selectively the first material from the un-masked portion up to the moment that a horizontal nanowire of the second material becomes suspended over a remaining portion of the unmasked portion, - forming a sacrificial layer on the remaining portion, while leaving the suspended horizontal nanowire uncovered, - providing, selectively, a cladding layer on the uncovered suspended horizontal nanowire, and thereafter - removing the sacrificial layer, the method further comprising: - forming a bottom horizontal nanowire by removing selectively the first material from the bottom layer of the un-masked portion up to the moment that the bottom horizontal nanowire of the second material becomes suspended, - removing the cladding layer covering the previously formed horizontal nanowires, wherein the sacrificial layer is a spin-on material and is self-planarizing and wherein the selective removal of the first material is cyclic and comprises: - oxidizing the first material and the second material, and - performing an etching process, whereby parameters of the etching process are chosen to remove the oxide of the first material faster than the oxide of the second material. - providing a substrate comprising a dielectric layer and a fin structure comprising a protruding portion protruding from the dielectric layer, the protruding portion comprising a multi-layer stack consisting of a layer of a first material stacked alternately and repeatedly with a layer of a second material, the bottom layer of the multilayer stack being a layer of the first material, - masking a part of the protruding portion including the top and the sidewalls thereof by providing a dielectric layer (1, 10) thereby creating an un-masked portion of the protruding portion, and - sequentially forming horizontal nanowires (11, 12, 13) starting from the top of the un-masked portion, wherein the forming is done by repeatedly performing a cycle comprising: - removing selectively the first material from the un-masked portion up to the moment that a horizontal nanowire of the second material becomes suspended over a remaining portion of the unmasked portion, - forming a sacrificial layer on the remaining portion, while leaving the suspended horizontal nanowire uncovered, - providing, selectively, a cladding layer on the uncovered suspended horizontal nanowire, and thereafter - removing the sacrificial layer, - forming a bottom horizontal nanowire by removing selectively the first material from the bottom layer of the un-masked portion up to the moment that the bottom horizontal nanowire of the second material becomes suspended, - removing the cladding layer covering the previously formed horizontal nanowires, wherein the sacrificial layer is a spin-on material and is self-planarizing and wherein the selective removal of the first material is cyclic and comprises: - oxidizing the first material and the second material, and - performing an etching process, whereby parameters of the etching process are chosen to remove the oxide of the first material faster than the oxide of the second material.