Semiconductor device comprising oxide semiconductor layer

A semiconductor device comprising a transistor, the transistor comprising:

• a gate electrode;
• a gate insulating layer over the gate electrode;
• and
• an oxide semiconductor layer, in which a channel is formed, over the gate insulating layer,
• wherein the oxide semiconductor layer comprises In, Sn, Ga, and Zn,
• wherein the oxide semiconductor layer comprises a first region comprising crystal grains, in which c-axes are oriented in a direction perpendicular or substantially perpendicular to a surface of the oxide semiconductor layer, in a superficial portion of the oxide semiconductor layer, and
• wherein the oxide semiconductor layer comprises a second region comprising an amorphous region which comprises a first microcrystal and a second microcrystal.

A semiconductor device comprising a transistor, the transistor comprising:

• an oxide semiconductor layer, in which a channel is formed;
• a gate insulating layer over the oxide semiconductor layer;
• and
• a gate electrode over the gate insulating layer,
• wherein the oxide semiconductor layer comprises In, Sn, Ga, and Zn,
• wherein the oxide semiconductor layer comprises a first region comprising crystal grains, in which c-axes are oriented in a direction perpendicular or substantially perpendicular to a surface of the oxide semiconductor layer, in a superficial portion of the oxide semiconductor layer, and
• wherein the oxide semiconductor layer comprises a second region comprising an amorphous region which comprises a first microcrystal and a second microcrystal.