Semiconductor device and method for manufacturing the semiconductor device

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first transistor comprising silicon;
• forming a first conductor over and electrically connected to the first transistor;
• forming a first insulator over the first conductor;
• forming a second insulator over the first insulator;
• forming a third insulator over the second insulator;
• forming a first opening in the second and third insulators to expose the first insulator;
• forming a second opening which includes the first opening and is in the first to third insulators to expose the first conductor;
• forming a second conductor which covers an inner wall and a bottom surface of the second opening;
• forming a third conductor over the second conductor;
• and
• forming a second transistor comprising an oxide semiconductor over the third conductor, the second transistor being electrically connected to the third conductor,
• wherein the first conductor is electrically connected to the third conductor through the second conductor, and
• wherein a top surface of the third insulator, a top surface of the second conductor, and a top surface of the third conductor are coplanar.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first transistor comprising a silicon substrate;
• forming a first conductor over and electrically connected to the first transistor;
• forming a first insulator over the first conductor;
• forming a second insulator over the first insulator;
• forming a third insulator over the second insulator;
• forming an opening in the first to third insulators;
• forming a second conductor which covers an inner wall and a bottom surface of the opening;
• forming a third conductor over the second conductor;
• and
• forming a second transistor comprising an oxide semiconductor layer over the third conductor, the second transistor being electrically connected to the third conductor,
• wherein the first conductor is electrically connected to the third conductor through the second conductor,
• wherein the second insulator is less permeable to hydrogen than the first insulator, and
• wherein the second conductor is less permeable to hydrogen than the third conductor.