A semiconductor structure includes a conductive structure over a first passivation layer. The semiconductor structure further includes a second passivation layer over the conductive structure and the first passivation layer. The second passivation layer includes a first oxide film extending along a top surface of the first passivation layer, sidewalls and a top surface of the conductive structure, wherein a top surface of the first oxide film is planar. The second passivation layer further includes a second oxide film over a top surface of the first oxide film and a top surface of the conductive structure, wherein a top surface of the second oxide film is planar. The second passivation layer further includes a third oxide film extending along a top surface of the second oxide film, the sidewalls and the top surface of the conductive structure, wherein a top surface of the third oxide film is curved.