An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574. The concentration of impurities such as water and hydrogen in the insulator 581 is preferably reduced as in the insulator 524 or the like.
Furthermore, a conductor 540a and a conductor 540b are positioned in openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductor 540a and the conductor 540b are provided to face each other with the conductor 560 therebetween. The structures of the conductor 540a and the conductor 540b are similar to a structure of a conductor 546 and a conductor 548 that will be described later.
An insulator 582 is provided over the insulator 581. A substance having a barrier property against oxygen or hydrogen is preferably used for the insulator 582. Therefore, a material similar to the material for the insulator 514 can be used for the insulator 582. For the insulator 582, a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide is preferably used, for example.