Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• an oxide semiconductor layer;
• a source electrode and a drain electrode connected to the oxide semiconductor layer;
• a gate insulating film;
• and
• a gate electrode adjacent to the oxide semiconductor layer with the gate insulating film therebetween,
• wherein the oxide semiconductor layer includes a nanocrystal with a size greater than or equal to 1 nm and smaller than or equal to 20 nm, and
• wherein a carrier concentration of the oxide semiconductor layer is smaller than or equal to 1×1012 cm3.

A semiconductor device comprising:

• an oxide semiconductor layer;
• a source electrode and a drain electrode connected to the oxide semiconductor layer;
• a gate insulating film;
• and
• a gate electrode adjacent to the oxide semiconductor layer with the gate insulating film therebetween,
• wherein the oxide semiconductor layer includes a nanocrystal, and
• wherein a c-axis of the nanocrystal is substantially perpendicular to a surface of the oxide semiconductor layer, and
• wherein a hydrogen concentration of the oxide semiconductor layer is smaller than or equal to 5×1019/cm3.

A semiconductor device comprising:

• an oxide semiconductor layer;
• a source electrode and a drain electrode connected to the oxide semiconductor layer;
• a gate insulating film;
• and
• a gate electrode adjacent to the oxide semiconductor layer with the gate insulating film therebetween,
• wherein the oxide semiconductor layer includes a nanocrystal,
• wherein a c-axis of the nanocrystal is substantially perpendicular to a surface of the oxide semiconductor layer, and
• wherein a carrier concentration of the oxide semiconductor layer is smaller than or equal to 1×1012 cm3.

A semiconductor device comprising:

• an oxide semiconductor layer;
• a source electrode and a drain electrode connected to the oxide semiconductor layer;
• an oxide region on a side surface of each of the source electrode and the drain electrode;
• a gate insulating layer;
• and
• a gate electrode adjacent to the oxide semiconductor layer with the gate insulating layer therebetween,
• wherein the source electrode and the drain electrode comprise a conductive material, and
• wherein the oxide region includes the conductive material.