Flash memory device and fabricating method thereof

A flash memory device comprising:

• a first insulating layer on a base insulating layer on a substrate;
• a lower wire layer that fills a trench in the first insulating layer;
• a first insulating interlayer and a second insulating layer stacked in sequence on the first insulating layer and the lower wire layer;
• a middle wire layer that fills a trench in the second insulating layer;
• and
• a second insulating interlayer and an upper wire layer stacked in sequence on the middle wire layer,
• wherein the lower wire layer, the middle wire layer and the upper wire layer are electrically connected to each other,
• wherein the first insulating layer includes a low-k layer in contact with the base insulating layer,
• wherein each of the first insulating interlayer, the second insulating layer, and the second insulating interlayer includes an FSG layer;
• and
• wherein a first FSG layer included in the first insulating interlayer and a second FSG layer included in the second insulating layer are formed in an interface between the middle wire layer and the first insulating interlayer.