Integrated circuit device

An integrated circuit device includes a substrate having a plurality of active regions defined therein, a first word line structure including a first word line, a first gate dielectric film surrounding the first word line, and an oxide semiconductor channel layer surrounding the first gate dielectric film, the first word line structure being buried in the substrate, and crossing a first active region of the plurality of active regions, a second word line structure including a second word line and a second gate dielectric film surrounding the second word line, the second word line structure being buried in the substrate and separated from the first word line structure, and crossing the first active region, a direct contact partially passing through the first active region and the first word line structure and contacting the oxide semiconductor channel layer, and a bit line contacting the direct contact.