Methods of fabricating semiconductor devices

A method of fabricating a semiconductor device, comprising:

• forming, on a substrate, a device isolation layer defining an active region;
• forming a buried gate in the active region;
• forming, on the substrate, a metal layer in contact with the active region;
• forming a first hard mask layer on the metal layer, a second hard mask layer on the first hard mask layer, and a photoresist layer on the second hard mask layer;
• patterning the photoresist layer to form a photoresist pattern;
• patterning the second hard mask layer using the photoresist pattern as an etching mask to form a second hard mask pattern;
• patterning the first hard mask layer using the second hard mask pattern as an etching mask to form a first hard mask pattern;
• and
• etching the metal layer using the first hard mask pattern and the second hard mask pattern as an etching mask to form a metal layer pattern,
• wherein the first hard mask layer includes impurity-doped amorphous silicon.

A method of fabricating a semiconductor device, comprising:

• sequentially forming a first hard mask layer, a second hard mask layer and a photoresist layer on a target layer, the first hard mask layer including an amorphous carbon layer and the second hard mask layer including impurity-doped amorphous silicon;
• patterning the photoresist layer to form a photoresist pattern;
• etching the second hard mask layer using the photoresist pattern as an etching mask to form a second hard mask pattern;
• and
• etching the first hard mask layer using the second hard mask pattern as an etching mask to form a first hard mask pattern.