| abstract |
A storage device with a small footprint is provided. In a memory cell including a read transistor, a write transistor, and a capacitor, a write transistor is provided above the read transistor. In addition, a read transistor may be provided above the write transistor. In addition, an oxide semiconductor is used as the semiconductor layer for forming the channel of the transistor for writing. An oxide semiconductor is used as the semiconductor layer forming the channel of the readout transistor. A plurality of memory cells are arranged in a matrix. |