Oxide semiconductor film and semiconductor device

An oxide semiconductor film comprising:

• a first layer comprising first nanocrystals;
• and
• a second layer on the first layer, the second layer comprising at least two crystals whose crystal axes are aligned,
• wherein the crystals in the second layer form a continuous lattice, and
• wherein, in the second layer, a region except for the crystals are a region in which first nanocrystals are mixed.

An oxide semiconductor film comprising:

• a first layer comprising first nanocrystals;
• and
• a second layer on the first layer, the second layer comprising at least two crystals whose crystal axes are aligned,
• wherein the crystals in the second layer form a continuous lattice, and
• wherein the crystals in the second layer are c-axis-oriented in a direction substantially perpendicular to the surface of the second layer.

semiconductor device comprising:

• a gate electrode layer;
• an oxide semiconductor layer by sputtering;
• a gate insulating layer between the gate electrode layer and the oxide semiconductor layer;
• a source electrode layer and a drain electrode layer in contact with the oxide semiconductor layer;
• and
• an oxide insulating layer over the source electrode layer and the drain electrode layer and in contact with a first region of a top surface of the oxide semiconductor layer,
• wherein the oxide semiconductor layer comprises a channel formation region,
• wherein the oxide semiconductor layer comprises In, Ga and Zn,
• wherein a carbon concentration of the oxide semiconductor layer is lower than 1×1021atoms/cm3,
• wherein at least a region of the oxide semiconductor layer includes crystals, and
• wherein each crystal has a structure which is c-axis-oriented in a direction substantially perpendicular to a surface of the oxide semiconductor layer at a location of the crystal.