Semiconductor device and memory device

A transistor comprising:

• a first oxide semiconductor film over an insulator;
• a second oxide semiconductor film over the first oxide semiconductor film;
• a third oxide semiconductor film over the first oxide semiconductor film;
• a fourth oxide semiconductor film over the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film;
• a gate insulating film over the fourth oxide semiconductor film;
• a gate electrode over the gate insulating film;
• and
• an insulating film over the gate electrode,
• wherein the second oxide semiconductor film and the third oxide semiconductor film comprise regions that face each other with the gate electrode positioned therebetween,
• wherein the gate insulating film comprises a region in contact with a top surface of the fourth oxide semiconductor film,
• wherein the first oxide semiconductor film comprises a first portion overlapping with the gate electrode with the second oxide semiconductor film positioned therebetween,
• wherein the first oxide semiconductor film comprises a second portion overlapping with the gate electrode with the third oxide semiconductor film positioned therebetween, and
• wherein the insulating film is in contact with the insulator.

A transistor comprising:

• a first fin to N-th fin, the N being a natural number of 2 or more, wherein the first fin comprises a first oxide semiconductor film and a second oxide semiconductor film, and a second fin comprises a third oxide semiconductor film and a fourth oxide semiconductor film;
• a fifth oxide semiconductor film over the first fin and the second fin;
• a gate insulating film over the fifth oxide semiconductor film;
• a gate electrode over the gate insulating film;
• an insulator below the first fin;
• and
• an insulating film over the gate electrode,
• wherein the first oxide semiconductor film and the third oxide semiconductor film comprise regions that face each other with the gate electrode positioned therebetween,
• wherein the second oxide semiconductor film and the fourth oxide semiconductor film comprise regions that face each other with the gate electrode positioned therebetween,
• wherein the second oxide semiconductor film comprises a first portion between the first oxide semiconductor film and the fifth oxide semiconductor film,
• wherein the gate electrode and the first portion overlap with each other with the gate insulating film positioned therebetween,
• wherein the fourth oxide semiconductor film comprises a second portion between the third oxide semiconductor film and the fifth oxide semiconductor film,
• wherein the gate electrode and the second portion overlap with each other with the gate insulating film positioned therebetween, and
• wherein the insulating film is in contact with the insulator.