A method for treating via sidewalls comprising the steps of providing a substrate having a number of metallic wires already formed; depositing a liner oxide layer; depositing an organic spin-on-glass layer; and depositing a second oxide layer. The second oxide layer is planarized by a chemical-mechanical polishing method. Photolithographic and etching methods, employing oxygen plasma treatment as well as a wet etching removal method are used to form vias above the metallic layers. A hydrogen plasma treatment is performed for the via sidewalls to prevent the occurrence of out-gassing and to obtain superior electrical properties. A titanium/titanium nitride film is deposited, and aluminium or tungsten is deposited into the vias and to form aluminium or tungsten plugs, thus completing the manufacturing process according to this invention. A semiconductor device formned by this method is also described.