Wiring structure, semiconductor device and methods of forming the same

A method of forming a wiring structure, the method comprising:

• forming a first contact plug through a first insulating interlayer formed on a semiconductor substrate;
• forming a second insulating interlayer on the first insulating interlayer;
• partially etching the first and second insulating interlayers, thereby forming first and second holes exposing an upper face of the first contact plug and an upper sidewall of the first contact plug;
• forming a protecting layer pattern encompassing the exposed upper sidewall of the first contact plug, the protecting layer pattern having an upper face at a height greater than an upper face of the first contact plug;
• and
• forming a second contact plug in the first and second holes, the second contact plug making electrical contact with the first contact plug.

A method of forming a wiring structure, the method comprising:

• forming a preliminary first insulating interlayer including a preliminary contact plug on semiconductor substrate;
• performing an etch-back process on an upper portion of the preliminary first insulating interlayer to form a first insulating interlayer covering a lower sidewall of the preliminary first contact plug such that an upper sidewall of the preliminary first contact plug is exposed;
• forming a protecting layer pattern on the first insulating interlayer, the protecting layer pattern having an upper face coplanar with an upper face of the preliminary first contact plug;
• performing an etch-back process on an upper portion of the preliminary first contact plug to form a first contact plug having a height lower than that of the preliminary first contact plug;
• forming a second insulating interlayer on the protecting layer pattern and the first insulating interlayer, the second insulating interlayer having a hole exposing a sidewall of the protecting layer pattern and an upper face of the first contact plug;
• and
• forming a second contact plug on the first contact plug to make electrical contact with the first contact plug, the second contact plug filling the hole.