Contact structure with arched top surface and fabrication method thereof

A method for forming a semiconductor device structure, comprising:

• forming a first dielectric layer over a substrate;
• forming a gate electrode layer in the first dielectric layer;
• recessing the gate electrode layer to form a recessed top surface lower than a top surface of the first dielectric layer;
• forming a first dielectric capping layer over the recessed top surface of the gate electrode layer, wherein a top width of the recessed top surface of the gate electrode layer is substantially equal to a top width of the first dielectric capping layer;
• forming an opening in the first dielectric layer to expose a source/drain region in the substrate;
• forming a first conductive layer in the opening;
• forming a conductive capping layer with an arched top surface in the opening and over the first conductive layer;
• and
• forming a second dielectric capping layer in the opening to cover the arched top surface of the conductive capping layer.

A method for forming a semiconductor device structure, comprising:

• forming a first dielectric layer over a substrate;
• forming a gate electrode layer in the first dielectric layer;
• forming an opening adjacent to the gate electrode layer and in the first dielectric layer;
• forming a first conductive layer in the opening;
• forming a conductive capping layer with a convex top surface in the opening, wherein a top width of the first conductive layer is substantially equal to a bottom width of the conductive capping layer;
• and
• forming a dielectric capping layer in the opening to cover the convex top surface of the conductive capping layer.