Display device and electronic unit

1. A display device comprising:

a substrate;

a display element;

a transistor as a drive element of the display element, and including a second semiconductor layer including an oxide semiconductor, a gate insulating film provided on a selected region in the second semiconductor layer, and a gate electrode provided on the gate insulating film in order of closeness to the substrate; and

a holding capacitance element holding electric charge corresponding to a video signal, and including a first conductive film, a first semiconductor layer including an oxide semiconductor, an insulating film, and a second conductive film in order of closeness to the substrate, wherein, both the first conductive film and the second semiconductor layer come into direct surface contact with the substrate, wherein

the display element, the transistor, and the holding capacitance element are provided on the substrate, wherein the first and second semiconductor layers are integrally formed of a same material on the substrate, wherein the second conductive film is formed of a same material as a material of the gate electrode, wherein the gate insulating film of the transistor and the insulating film of the holding capacitance element are separated from one another by a gap, and wherein the gate electrode is formed in a same element layer as the second conductive film.

2. The display device according to claim 1 , wherein the transistor further includes

a source drain electrode layer being electrically connected to the second semiconductor layer in order of closeness to the substrate.

3. The display device according to claim 2 , wherein the first conductive film is provided on a selected region in the substrate, and the insulating film is formed of a same material as a material of the gate insulating film.

4. The display device according to claim 2 , wherein the first and second semiconductor layers have a low-resistance region having a lower electric resistance than other regions in a region unopposed to both the holding capacitance element and the gate electrode, and

the source/drain electrode layer is electrically connected to the low-resistance region.

5. The display device according to claim 2 , wherein a high-resistance film is provided covering the holding capacitance element, the gate electrode, and the low resistance region of the first and second semiconductor layers.

6. The display device according to claim 1 , wherein the display element is an organic electroluminescence element.

7. The display device according to claim 1 , wherein the display element is a liquid crystal display element.

8. An electronic unit with a display device, the display device comprising:

a substrate;

a display element;

a transistor as a drive element of the display element, and including

a second semiconductor layer including an oxide semiconductor,

a gate insulating film provided on a selected region in the second semiconductor layer, and

a gate electrode provided on the gate insulating film in order of closeness to the substrate; and

a holding capacitance element holding electric charge corresponding to a video signal, and including a first conductive film, a first semiconductor layer including an oxide semiconductor, an insulating film, and a second conductive film in order of closeness to the substrate, wherein, both the first conductive film and the second semiconductor layer come into direct surface contact with the substrate, and wherein

the display element, the transistor, and the holding capacitance element are provided on the substrate, wherein the first and second semiconductor layers are integrally formed of a same material on the substrate, wherein the second conductive film is formed of a same material as a material of the gate electrode, wherein the gate insulating film of the transistor and the insulating film of the holding capacitance element are separated from one another by a gap, and wherein the gate electrode is formed in a same element layer as the second conductive film.