A semiconductor device includes: a first stacked structure including a first lower dielectric layer, a first horizontal gate structure, and a first upper dielectric layer stacked vertically; a second stacked structure including a second lower dielectric layer, a second horizontal gate structure, and a second upper dielectric layer stacked vertically, and having a first side facing a first side of the first stacked structure; a first channel layer formed on the first side of the first stacked structure; a second channel layer formed on the first side of the second stacked structure; a lower electrode layer commonly coupled to lower ends of the first and second channel layers between the first and second stacked structures; a first upper electrode layer coupled to an upper end of the first channel layer; and a second upper electrode layer coupled to an upper end of the second channel layer.