US Patent 9865736 Semiconductor devices and methods of manufacturing the same

A semiconductor device includes a gate structure on a substrate, a source/drain layer on a portion of the substrate adjacent the gate structure, a first contact plug contacting an upper surface of the source/drain layer, and a second contact plug contacting upper surfaces of the gate structure and the first contact plug. A bottom surface of the second contact plug has a first portion not contacting the upper surface of the first contact plug, and the first portion is higher than the upper surface of the gate structure.