MEMORY DEVICE HAVING BURIED BIT LINE AND VERTICAL TRANSISTOR AND FABRICATION METHOD THEREOF

摘要

A method of forming a buried bit line is provided. A substrate is provided and a line-shaped trench region is defined in the substrate. A line-shaped trench is formed in the line-shaped trench region of the substrate. The line-shaped trench includes a sidewall surface and a bottom surface. Then, the bottom surface of the line-shaped trench is widened to form a curved bottom surface. Next, a doping area is formed in the substrate adjacent to the curved bottom surface. Lastly, a buried conductive layer is formed on the doping area such that the doping area and the buried conductive layer together constitute the buried bit line.