An embodiment of the disclosure provides a semiconductor device. The semiconductor device includes a plurality of metallization layers comprising a topmost metallization layer. The topmost metallization layer has two metal features having a thickness T1 and being separated by a gap. A composite passivation layer comprises a HDP CVD oxide layer under a nitride layer. The composite passivation layer is disposed over the metal features and partially fills the gap. The composite passivation layer has a thickness T2 about 20% to 50% of the thickness T1.