Method of fabricating semiconductor device

A method for manufacturing a semiconductor device, comprising:

• forming a conductive layer, a buffer layer and a hard mask layer on the first dielectric layer;
• forming a patterned mask layer on the hard mask layer;
• using a patterned mask layer as a mask, performing a first etching process to pattern the hard mask layer and the buffer layer, and to form a recess in the conductive layer;
• removing the patterned mask layer;
• selectively removing a portion of the buffer layer to expose a top corner of the recess;
• performing a second etching process to round the top corner of the recess;
• performing a third etching process to remove the conductive layer exposed from a bottom surface of the recess to form a plurality of conductive lines having rounding top corners;
• removing the hard mask layer and the buffer layer;
• and
• forming a second dielectric layer on the plurality of conductive lines and between the plurality of conductive lines.