Semiconductor device and method for manufacturing the same

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first insulating layer comprising silicon nitride over a substrate;
• forming a first conductive layer comprising copper over the first insulating layer;
• forming a second conductive layer over the first conductive layer so as to cover the first conductive layer;
• forming a second insulating layer comprising silicon nitride over the second conductive layer;
• forming a third insulating layer comprising silicon oxide over the second insulating layer;
• forming an island-like oxide semiconductor layer over the third insulating layer;
• forming third conductive layers functioning as a source electrode and a drain electrode over the island-like oxide semiconductor layer;
• forming a fourth insulating layer comprising silicon oxide over the third conductive layers;
• forming a fifth insulating layer comprising silicon nitride over the fourth insulating layer;
• forming a fourth conductive layer so as to be electrically connected to one of the third conductive layers functioning as the source electrode and the drain electrode through an opening provided in the fourth insulating layer and the fifth insulating layer;
• forming a fifth conductive layer comprising copper over the fourth conductive layer;
• forming a sixth insulating layer comprising silicon nitride so as to cover the fifth conductive layer;
• and
• forming a sixth conductive layer so as to be electrically connected to the other of the third conductive layers functioning as the source electrode and the drain electrode through an opening provided in the fourth insulating layer, the fifth insulating layer, and the sixth insulating layer,
• wherein a first heat treatment is performed so that hydrogen concentration of the island-like oxide semiconductor layer is decreased, and
• wherein the first conductive layer and the fifth conductive layer do not overlap with the island-like oxide semiconductor layer.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first conductive layer comprising copper over a substrate;
• forming a first insulating layer comprising nitrogen over the first conductive layer;
• forming a second insulating layer comprising oxygen over the first insulating layer;
• forming an oxide semiconductor layer over the second insulating layer;
• forming a second conductive layer over the oxide semiconductor layer, wherein the second conductive layer comprises one selected from the group consisting of W, Ta, Mo, Ti and Cr;
• forming a third conductive layer comprising copper over the second conductive layer, wherein the third conductive layer is electrically connected to the oxide semiconductor layer;
• and
• forming a fourth conductive layer electrically connected to the oxide semiconductor layer, wherein the fourth conductive layer comprises a transparent conductive material.