Semiconductor devices having contact plugs with stress buffer spacers and methods of fabricating the same

A method of manufacturing a semiconductor device comprising:

• providing a semiconductor substrate;
• forming a first insulator on the substrate;
• forming a contact hole penetrating the first insulator;
• covering a sidewall of the contact hole with a second insulator, wherein the second insulator has a density lower than a density of the first insulator;
• epitaxially growing a semiconductor material within the contact hole;
• and
• forming a metal plug in the contact hole, wherein the metal plug is electrically connected to the epitaxially grown semiconductor material.

A method of manufacturing a semiconductor device comprising:

• forming an impurity region in a semiconductor substrate;
• forming a conductive layer on the semiconductor substrate;
• forming a first insulating layer on the first conductive layer;
• forming a conductive contact plug penetrating the first insulating layer and electrically connected to the impurity region, the conductive contact plug being confined to an area directly above the impurity region;
• and
• forming a second insulating layer between the conductive contact plug and the first insulating layer, the first insulating layer being denser than the second insulating layer,
• wherein the conductive contact plug comprises a semiconductor plug being directly connected to the impurity region and a metal directly connected to the semiconductor plug,
• wherein the semiconductor plug is epitaxial grown from the semiconductor substrate.

A method of manufacturing a semiconductor device comprising:

• forming a conductive region in a semiconductor substrate;
• forming a conductive layer on the semiconductor substrate;
• forming a first insulating layer on the first conductive layer;
• forming a contact hole penetrating the first insulating layer and exposing a portion of the first conductive region, the contact hole being confined to an area directly above the first conductive region;
• forming a second insulating layer on a sidewall of the contact hole;
• forming a lower plug epitaxially growing in a lower portion of the contact hole;
• and
• forming an upper plug in an upper portion of the contact hole, the upper plug being electrically connected to the lower plug.