Semiconductor device and semiconductor memory device

A semiconductor device, comprising:

• a first electrode;
• a second electrode;
• an oxide semiconductor layer provided between the first electrode and the second electrode;
• a gate electrode surrounding the oxide semiconductor layer;
• and
• a gate insulating layer provided between the gate electrode and the oxide semiconductor layer,
• wherein the oxide semiconductor layer includes:
• a first region of a first conductive type facing the gate electrode;
• a second region of the first conductive type provided between the first region and the first electrode;
• and
• a third region of the first conductive type provided between the first region and the second electrode,
• the gate electrode includes:
• a first layer containing a first material having a first work function;
• a second layer provided on a first electrode side with respect to the first layer and containing a second material having a second work function;
• and
• a third layer provided on a second electrode side with respect to the first layer and containing a third material having a third work function,
• when the first conductive type is n-type, the second work function is smaller than the first work function, and the third work function is smaller than the first work function, and
• when the first conductive type is p-type, the second work function is larger than the first work function, and the third work function is larger than the first work function.