| 摘要 |
Provided is a transistor including an oxide semiconductor in a channel formation region in which the threshold voltage is controlled, which is a so-called normally-off switching element. The switching element includes a first insulating film, an oxide semiconductor layer over the first insulating film and includes a channel formation region, a second insulating film covering the oxide semiconductor layer, a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer. The semiconductor device further includes a first gate electrode layer overlapping the channel formation region with the first insulating film therebetween, a second gate electrode layer overlapping the channel formation region with the second insulating film therebetween, and a third gate electrode layer overlapping a side surface of the oxide semiconductor layer in a channel width direction with the second insulating film therebetween. |
