| abstract |
A semiconductor device having good electrical properties and reliability is provided. Forming a first insulator, forming a second insulator over the first insulator, forming an island-shaped oxide over the second insulator, forming a stack of a third insulator and a conductor over the oxide, over the oxide and the laminate By forming a film having a metal element, the oxide is selectively lowered in resistance, and after forming a fourth insulator on the second insulator, oxide, and stack, an opening is formed to expose the second insulator to the fourth insulator, and the second A fifth insulator is formed on the insulator and the fourth insulator, and oxygen introduction treatment is performed on the fifth insulator. |