A stack with excellent electrical characteristics and reliability is provided. The stack includes an insulator, a conductor, and a first oxide between the insulator and the conductor; the first oxide includes a first c-axis-aligned crystal region; and a c-axis of the first crystal region is substantially perpendicular to a plane of the first oxide on the insulator side. Alternatively, the stack includes an insulator, a conductor, a first oxide between the insulator and the conductor, and a second oxide facing the first oxide with the insulator therebetween; the first oxide includes a first c-axis-aligned crystal region; a c-axis of the first crystal region is substantially perpendicular to a plane of the first oxide on the insulator side; the second oxide includes a second c-axis-aligned crystal region; and a c-axis of the second crystal region is substantially perpendicular to a plane of the second oxide on the insulator side.