Methods of manufacturing integrated circuit devices having reduced contact resistance between a substrate and a contact pad while maintaining separation of the substrate and the contact pad and integrated circuit devices formed thereby

A contact structure, which connects a source/drain region of a substrate between two gate patterns isolated from each other at a predetermined distance to an upper conductive layer comprising:

• an insulating layer, which is formed at the sidewalls of each of the gate patterns, has a bottom portion extending over the substrate to a predetermined length and exposes a portion of the source/drain region of the substrate between the two gate patterns;
• a lower pad layer, which is formed of the same material as the substrate at the exposed source/drain region to be thicker than the insulating layer by epitaxial growth and has a sidewall isolated from the sidewall of the insulating layer;
• and
• an upper conductive layer, which is formed of a conductive material filling the space between the two gate patterns, defined by the insulating layer and the lower pad layer.

A semiconductor device comprising:

• a semiconductor substrate at which a source/drain region is formed;
• a pair of gate patterns formed on the substrate on adjacent sides of the source/drain region, respectively;
• an insulating layer formed at the sidewalls of the gate patterns, having a bottom side, which extends over the substrate and exposing a portion of the source/drain region of the substrate;
• a lower pad layer which is formed to be thicker than the insulating layer on the surface of the exposed source/drain region by epitaxially growing the same material as the substrate and has a sidewall isolated from the sidewall of the insulating layer;
• and
• an upper conductive layer which is formed of a conductive material filling the space between the gate patterns, defined by the insulating layer and the lower pad layer.