Semiconductor device and method of fabricating the same

A semiconductor device, comprising:

• a semiconductor substrate that includes a trench defining an active region;
• a buried dielectric pattern in the trench;
• a silicon oxide layer between the buried dielectric pattern and an inner wall of the trench;
• a polycrystalline silicon layer between the silicon oxide layer and the inner wall of the trench;
• a conductive line that is in the semiconductor substrate and runs across the active region;
• a gate dielectric layer between the semiconductor substrate and the conductive line;
• and
• a plurality of impurity regions in the active region on opposite sides of the conductive line,
• wherein the polycrystalline silicon layer has a first surface in contact with the silicon oxide layer, and
• wherein the first surface includes a plurality of silicon grains that are uniformly distributed.