Semiconductor Device And Method For Manufacturing The Semiconductor Device

A semiconductor device comprising:

• a first conductive layer;
• a second conductive layer;
• a third conductive layer;
• a fourth conductive layer;
• an oxide semiconductor layer;
• a first insulating layer;
• a second insulating layer;
• and
• a third insulating layer,
• wherein the first insulating layer is positioned over the first conductive layer,
• wherein the second conductive layer is positioned over the first insulating layer,
• wherein the first insulating layer and the second conductive layer comprise a first opening reaching the first conductive layer,
• wherein the oxide semiconductor layer is in contact with at least a top surface of the first conductive layer, a side surface of the first insulating layer, and a side surface of the second conductive layer, in the first opening,
• wherein the second insulating layer is positioned over the oxide semiconductor layer in the first opening,
• wherein the third conductive layer overlaps with the oxide semiconductor layer with the second insulating layer therebetween in the first opening,
• wherein the third insulating layer is positioned over the second insulating layer and over the third conductive layer,
• wherein the fourth conductive layer is positioned over the third insulating layer and is in contact with a top surface of the third conductive layer,
• wherein the second conductive layer overlaps with the fourth conductive layer with the third insulating layer therebetween, and
• wherein, in a cross-sectional view, a maximum value of a width of the third conductive layer is smaller than or equal to a minimum value of a width of the first opening in the second conductive layer.

A method for manufacturing a semiconductor device, comprising:

• forming a first conductive layer;
• forming a first insulating film over the first conductive layer;
• forming, over the first insulating film, a second conductive layer comprising a first opening in a region overlapping with the first conductive layer;
• processing the first insulating film to form a first insulating layer comprising a second opening reaching the first conductive layer;
• forming an oxide semiconductor layer in contact with a top surface of the first conductive layer, a side surface of the first insulating layer, and a top surface and a side surface of the second conductive layer;
• forming a second insulating layer over the oxide semiconductor layer;
• forming a conductive film over the second insulating layer;
• forming, over the conductive film, a mask overlapping with the first opening and not overlapping with the second conductive layer;
• and
• processing the conductive film using the mask to form a third conductive layer,
• wherein a maximum value of a width of the third conductive layer is smaller than or equal to a minimum value of a width of the first opening in a cross-sectional view.