Semiconductor device

A semiconductor device comprising:

• a memory cell comprising:
• a first transistor, a channel formation region of the first transistor comprising a first oxide semiconductor layer;
• and
• a capacitor,
• wherein a gate of the first transistor is electrically connected to a word line,
• wherein one of a source and a drain of the first transistor is electrically connected to a bit line,
• wherein the other of the source and the drain of the first transistor is electrically connected to one electrode of the capacitor,
• wherein the other electrode of the capacitor is electrically connected to a capacitor line, and
• wherein an off-state current per micrometer of a channel width of the first transistor is 100 zA/μm or less at room temperature.

A semiconductor device comprising:

• a memory cell comprising:
• a first transistor, a channel formation region of the first transistor comprising a first oxide semiconductor layer;
• and
• a capacitor comprising a second oxide semiconductor layer,
• wherein a gate of the first transistor is electrically connected to a word line,
• wherein one of a source and a drain of the first transistor is electrically connected to a bit line,
• wherein the other of the source and the drain of the first transistor is electrically connected to one electrode of the capacitor,
• wherein the other electrode of the capacitor is electrically connected to a capacitor line, and
• wherein an off-state current per micrometer of a channel width of the first transistor is 100 zA/μm or less at room temperature.