Semiconductor device

A semiconductor device, comprising:

• a first transistor including:
• a first electrode;
• a first insulating layer above the first electrode, the first insulating layer having a first sidewall;
• a first oxide semiconductor layer on the first sidewall, the first oxide semiconductor layer being connected with a top surface of the first electrode;
• a first gate electrode facing the first oxide semiconductor layer;
• a first gate insulating layer between the first oxide semiconductor layer and the first gate electrode;
• a second electrode above the first insulating layer, the second electrode being connected with a top surface of the first oxide semiconductor layer;
• and
• a first assisting electrode on the first insulating layer, the first assisting electrode being connected with a bottom surface of the first oxide semiconductor layer;
• and
• a second transistor including:
• a third electrode;
• a fourth electrode separated from the third electrode;
• a second oxide semiconductor layer between the third electrode and the fourth electrode, the second oxide semiconductor layer being connected with a top surface of each of the third electrode and the fourth electrode;
• a second gate electrode facing the second oxide semiconductor layer;
• and
• a second gate insulating layer between the second oxide semiconductor layer and the second gate electrode.