| abstract |
A semiconductor device using a transistor having favorable operation characteristics and having improved operation characteristics is provided. In a transistor, an outer edge of an oxide semiconductor layer is covered with an electrode functioning as one of a source electrode and a drain electrode; over the oxide semiconductor layer, a gate insulating layer is provided; A gate electrode 105 having an annular planar shape is formed. The electrode 108, which is the other of the source electrode and the drain electrode, is surrounded by an annular gate electrode 105 outside the electrode 108. The annular gate electrode 105 has the outside of the annular gate electrode 105 as one of a source electrode and a drain electrode. It is surrounded by functioning electrodes 104. A channel formation region of the transistor 110 is formed in a region which overlaps with the gate electrode 105 with the gate insulating layer 103 interposed therebetween, between the electrodes 104 and 108 which are a source electrode and a drain electrode. [Selection diagram] Fig. 1 |