The present disclosure provides a method for forming a semiconductor structure. In accordance with some embodiments, the method includes providing a substrate and a conductive feature formed over the substrate; forming a first etch stop layer over the conductive feature; forming a low-k dielectric layer over the first etch stop layer; etching the low-k dielectric layer to form a contact trench aligned with the conductive feature; performing a sputtering process to the first etch stop layer exposed in the contact trench; and forming a sealing oxide layer on the low-k dielectric layer. In some embodiments, the sealing oxide layer is self-aligned and conformed to surfaces of the low-k dielectric layer exposed in the contact trench.