Transistor with zro or hfo gate insulator sandwiched between two sio or aio gate insulators over an oxide semiconductor film

Abstract

To provide a semiconductor device which includes a gate insulating film with high withstand voltage and thus can have high reliability. The semiconductor device includes an oxide semiconductor film over an insulating surface; a pair of first conductive films over the oxide semiconductor film; a first insulating film, a second insulating film, and a third insulating film which are stacked in this order over the oxide semiconductor film and the pair of first conductive films; and a second conductive film overlapping with the oxide semiconductor film over the first to third insulating films. The first insulating film and the third insulating film contain silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, or aluminum oxynitride. The second insulating film contains gallium oxide, zirconium oxide, or hafnium oxide.