A method of forming a low-k dielectric layer and forming a structure in the low-k dielectric layer includes depositing a low-k dielectric layer over a substrate, performing a first treatment to the low-k dielectric layer, performing post-formation processes, and performing a second treatment to the low-k dielectric layer. The k value of the low-k dielectric layer is lowered by the first treatment. The post-formation processes performed to the low-k dielectric layer include at least one low-k dielectric material damaging process. The second treatment restores the low-k dielectric layer. Preferably, each of the first and second treatments includes a curing process selected from e-beam curing, ultraviolet curing, plasma curing, SCCO.sub.2 cleaning, and combinations thereof.