Borderless contact structure and method of forming the same

A method of forming a borderless contact structure, the method comprising:

• selectively etching a predetermined portion of a semiconductor substrate to form a trench defining an active region having a top surface;
• forming a device isolation region in the trench, the device isolation region having a protrusion which is higher in level than the top surface of the active region;
• forming a gate pattern on the active region;
• forming a lightly doped drain (LDD) region in the active region on both sides of the gate pattern;
• forming an insulating layer for forming a spacer on the resultant structure including the LDD region;
• anisotropic etching the insulating layer for forming a spacer to form a gate spacer on a sidewall of the gate pattern and to form an etch stop spacer on the sidewall of the protrusion of the device isolation region;
• forming an impurity diffusion region in the active region;
• sequentially forming an etch stop layer and an interlayer insulating layer over the resultant structure,
• wherein the insulating layer for forming a spacer is formed of a material having an etching selectivity with respect to the interlayer insulating layer;
• and
• successively patterning the interlayer insulating layer and the etch stop layer to form a contact hole exposing at least a portion of the impurity diffusion region.