Methods of manufacturing semiconductor devices having contact plugs in insulation layers

A method of manufacturing a semiconductor device, the method comprising:

• forming a first interlayer insulation layer on a substrate that includes a first active region and a second active region;
• patterning the first interlayer insulation layer to form a first opening that exposes the first active region and a second opening that exposes the second active region;
• depositing a first conductive layer in the first and second openings and on the first interlayer insulation layer;
• patterning the first conductive layer to form a first contact plug and a second contact plug, wherein a height of a top surface of the second contact plug from the substrate is greater than a height of a top surface of the first contact plug from the substrate;
• forming a second interlayer insulation layer on the first interlayer insulation layer and the first contact plug, wherein a top surface of the second interlayer insulation layer is coplanar with the top surface of the second contact plug;
• forming a third contact plug on the second contact plug that is electrically connected to the second contact plug, wherein a silicide layer is formed at an interface between the second contact plug and third contact plug, wherein a height of a lower surface of the silicide layer from the substrate is greater than a height of an upper surface of the first contact plug from the substrate;
• forming a capping layer on the third contact plug;
• forming a first spacer on a side surface of the third contact plug, wherein the first spacer covers an entirety of a side portion of the silicide layer and extends from the silicide layer to the second contact plug;
• forming a third interlayer insulation layer on the second interlayer insulation layer, the third interlayer insulation layer covering the third contact plug;
• patterning the third interlayer insulation layer to form a third opening that exposes the first contact plug;
• and
• forming a fourth contact plug that is electrically connected to the first contact plug by depositing a third conductive material in the third opening.