a method of forming a high aspect ratio via opening through multiple dielectric layers , a high aspect ratio electrically conductive via , methods of forming three - dimension integrated circuits , and three - dimensional integrated circuits . the methods include forming a stack of at least four dielectric layers and etching the first and third dielectric layers with processes selective to the second and fourth dielectric layers , etching the second and third dielectric layers with processes selective to the first and second dielectric layers . advantageously the process used to etch the third dielectric layer is not substantially selective to the first dielectric layer .