Semiconductor device and method for fabricating the semiconductor device

A semiconductor device comprising:

• a semiconductor layer, a first conductive layer, a second conductive layer, a third conductive layer, a fourth conductive layer, a first insulating layer, a second insulating layer, a third insulating layer and a fourth insulating layer,
• wherein the first insulating layer is over the first conductive layer,
• wherein the first insulating layer comprises a first opening overlapping with the first conductive layer,
• wherein the second conductive layer is over the first insulating layer,
• wherein the second conductive layer comprises a second opening overlapping with the first opening,
• wherein the second insulating layer is over the second conductive layer,
• wherein the second insulating layer comprises a third opening overlapping with the first opening,
• wherein the third conductive layer is over the second insulating layer,
• wherein the third conductive layer comprises a fourth opening overlapping with the first opening,
• wherein the third insulating layer is in contact with a sidewall of the first opening, a sidewall of the second opening, and a sidewall of the third opening,
• wherein the semiconductor layer is in contact with a top surface of the first conductive layer, a side surface of the third insulating layer, and a top surface of the third conductive layer,
• wherein the fourth insulating layer is over the semiconductor layer,
• wherein the fourth conductive layer is over the fourth insulating layer,
• wherein the third insulating layer comprises a region between the sidewall of the first opening in the first insulating layer and the semiconductor layer, and
• wherein the semiconductor layer comprises a region between the sidewall of the second opening in the second conductive layer and the fourth conductive layer.

A method for fabricating a semiconductor device, comprising:

• forming a first conductive film;
• partly removing the first conductive film to form a first conductive layer;
• forming a first insulating film over the first conductive layer;
• forming a second conductive film over the first insulating film;
• partly removing the second conductive film to form a second conductive layer;
• forming a second insulating film over the second conductive layer;
• forming a third conductive film over the second insulating film;
• forming a resist mask over the third conductive film by photolithography;
• removing a region that is in the third conductive film and does not overlap with the resist mask by etching to provide a first opening;
• removing a region that is in the second insulating film and does not overlap with the resist mask by etching to provide a second opening;
• removing a region that is in the second conductive layer and does not overlap with the resist mask by etching to provide a third opening;
• removing a region that is in the first insulating film and does not overlap with the resist mask by etching to provide a fourth opening and to expose a top surface of the first conductive layer;
• forming a third insulating film to cover a top surface of the third conductive film, the exposed top surface of the first conductive layer, a sidewall of the first opening, a sidewall of the second opening, a sidewall of the third opening, and a sidewall of the fourth opening;
• and
• processing the third insulating film by anisotropic etching to form a sidewall insulating layer covering the sidewall of the third opening.