A memory device including a word line, a source line, a bit line, a memory layer, a channel material layer is described. The word line extends in a first direction, and liner layers disposed on a sidewall of the word line. The memory layer is disposed on the sidewall of the word line between the liner layers and extends along sidewalls of the liner layers in the first direction. The liner layers are spaced apart by the memory layer, and the liner layers are sandwiched between the memory layer and the word line. The channel material layer is disposed on a sidewall of the memory layer. A dielectric layer is disposed on a sidewall of the channel material layer. The source line and the bit line are disposed at opposite sides of the dielectric layer and disposed on the sidewall of the channel material layer. The source line and the bit line extend in a second direction perpendicular to the first direction. A material of the liner layers has a dielectric constant lower than that of a material of the memory layer.