Patent ID: 9741794
Date: 2017-08-22
CPC Classifications: H01L

Claim:
1. A semiconductor device comprising: a first oxide semiconductor film over an insulating surface; a second oxide semiconductor film over the first oxide semiconductor film; a third oxide semiconductor film over the second oxide semiconductor film; a source electrode and a drain electrode each in direct contact with side surfaces of the first oxide semiconductor film, the second oxide semiconductor film, and the third oxide semiconductor film and a portion of a top surface of the third oxide semiconductor film; a gate insulating film over the third oxide semiconductor film, the source electrode, and the drain electrode; a gate electrode over and in direct contact with the gate insulating film; and an oxide insulating film over and in direct contact with the source electrode, the drain electrode, a side surface of the gate insulating film, and the gate electrode, wherein the gate electrode faces a top surface and a side surface of the second oxide semiconductor film and a portion of a side surface of the first oxide semiconductor film with at least the gate insulating film interposed therebetween, and wherein a length of a region where the second oxide semiconductor film and the source electrode or the drain electrode overlap with each other in a channel length direction is shorter than twice a length between the source electrode and the drain electrode on the third oxide semiconductor film.