Abstract: A semiconductor device having a structure which can prevent a decrease in electrical characteristics due to miniaturization is provided. The semiconductor device includes, over an insulating surface, a stack in which a first oxide semiconductor layer and a second oxide semiconductor layer are sequentially formed, and a third oxide semiconductor layer covering part of a surface of the stack. The third oxide semiconductor layer includes a first layer in contact with the stack and a second layer over the first layer. The first layer includes a microcrystalline layer, and the second layer includes a crystalline layer in which c-axes are aligned in a direction perpendicular to a surface of the first layer.

Abstract: A process for heat-treating an object in a heat-treating apparatus comprises carburizing the object under a carburizing gas atmosphere in a carburizing zone, cooling the object with a cooling gas, and nitriding the object under a nitriding gas atmosphere in a nitriding zone.

Abstract: A heat-treating apparatus comprises zones such as a carburizing zone, a cooling zone, and a nitriding zone, those zones are formed in series by partitioning a continuous passage through doors, and conveyance means for conveying an object along the passage. The cooling zone comprises a forced-feed cooling means for cooling the object by blowing cooling gas.