A novel semiconductor device is provided. The semiconductor device includes an oxide semiconductor as a first semiconductor, silicon as a second semiconductor, and a plurality of memory cells lined up in a first direction; and a memory cell includes a writing transistor and a reading transistor. The first semiconductor and the second semiconductor extend in the first direction, part of the first semiconductor functions as a channel formation region of the writing transistor, and part of the second semiconductor functions as a channel formation region of the reading transistor. The second semiconductor includes a region in contact with a first layer containing a first metal element.