Semiconductor device and manufacturing method thereof

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

• forming a source electrode and a drain electrode over a substrate having an insulating surface;
• forming an oxide semiconductor layer covering an end portion of the source electrode and an end portion of the drain electrode;
• adding a halogen element into the oxide semiconductor layer;
• performing first heat treatment on the oxide semiconductor layer after the addition of the halogen element;
• forming a gate insulating layer overlapping with the end portion of the source electrode and the end portion of the drain electrode and in contact with the oxide semiconductor layer after performing the first heat treatment;
• and
• forming a gate electrode overlapping with the end portion of the source electrode and the end portion of the drain electrode and in contact with the gate insulating layer.

A semiconductor device comprising:

• a gate electrode over an insulating surface;
• a gate insulating layer over the insulating surface and the gate electrode;
• an oxide semiconductor layer having a halogen element over the gate insulating layer;
• a source electrode and a drain electrode over the gate insulating layer and the oxide semiconductor layer;
• and
• an insulating layer in contact with part of the oxide semiconductor layer and over the gate insulating layer, the oxide semiconductor layer, the source electrode, and the drain electrode,
• wherein a concentration of the halogen element is higher than or equal to 1015 atoms/cm3 and lower than or equal to 1018 atoms/cm3.

A semiconductor device comprising:

• a source electrode and a drain electrode over an insulating surface;
• an oxide semiconductor layer having a halogen element over the insulating surface, the source electrode, and the drain electrode;
• a gate insulating layer over the insulating surface, the source electrode, the drain electrode, and the oxide semiconductor layer;
• and
• a gate electrode over the gate insulating layer,
• wherein a concentration of the halogen element is higher than or equal to 1015 atoms/cm3 and lower than or equal to 1018 atoms/cm3.