Semiconductor structure and method for forming the same

A method for forming a semiconductor structure, comprising:

• forming a fin structure over a substrate;
• growing a source/drain epitaxial structure over the fin structure;
• forming a contact structure over the source/drain epitaxial structure;
• forming an inter-layer dielectric (ILD) structure over the contact structure and a gate structure;
• forming a first via structure in the ILD structure over the contact structure;
• forming a metal line over the first via structure and the ILD structure;
• forming a hard mask layer over the metal line, wherein a distance between a top surface and a bottom surface of the hard mask layer varies from a center to an edge of the hard mask layer;
• depositing a spacer layer covering the hard mask layer and a top surface of the ILD structure;
• depositing a dielectric layer over and between the metal line;
• etching the dielectric layer to form an opening exposing the spacer layer;
• etching through the spacer layer from the opening to expose the metal line;
• and
• forming a second via structure in the opening.

A method for forming a semiconductor structure, comprising:

• forming a gate structure over a substrate;
• forming source/drain epitaxial structures on opposite sides of the gate structure;
• forming a contact structure over the source/drain epitaxial structure;
• forming a first via structure over the contact structure;
• forming a metal line electrically connected to the first via structure;
• forming a hard mask layer over the metal line;
• forming a spacer layer over a sidewall and over a portion of a top surface of the metal line;
• and
• forming a second via structure over the metal line through the spacer layer, wherein the second via structure is in contact with the metal line through the hard mask layer.