A tree-structure memory device including a plurality of bit lines formed on a substrate and arranged in at least one plane substantially parallel to a substrate surface and extending substantially in a first direction, a plurality of layers having a plurality of memory cells arranged in a first array, a tree structure corresponding to a plurality of layers and a bit line; and a word-line group including at least one word line crossing with the tree structure, a memory cell of the first array being located at the first intersection region in a layer of said layers.