Thin film transistor and matrix display device

A thin film transistor comprising:

• a semiconductor layer made of ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO or ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO that have been doped with (a) an element that can be univalent or (b) Ni;
• and
• a gate insulating film, wherein
• the gate insulating film includes:
• a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode;
• and
• a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that has an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer, the second insulating film being made of KNbO3, KTaO3, BaTiO3, CaSO3, CaZrO3, CdSnO3, SrHfO3, SrSnO3, SrTiO3, YScO3, CaHfO3, MgCeO3, SrCeO3, BaCeO3, SrZrO3, BaZrO3, LiGaO2, mixed crystal (Li1−(x+y)NaxKy)(Ga1−zAlz)O2 of LiGaO2, or a solid solution having at least two of these oxides.

A matrix display device comprising switching elements disposed in a matrix manner, wherein

• each of the switching elements is constituted of a thin film transistor that includes:
• a semiconductor layer made of ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO or ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO that have been doped with (a) an element that can be univalent or (b) Ni;
• and a gate insulating film, wherein the gate insulating film has:
• a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode;
• and a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that is made of an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer.

A matrix display device comprising switching elements disposed in a matrix manner, wherein

• each of the switching elements is constituted of a thin film transistor that includes:
• a semiconductor layer made of ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO or ZnO, Mgx Zn1−x O, Cdx Zn1−x O or CdO that have been doped with (a) an element that can be univalent or (b) Ni;
• and a gate insulating film, wherein the gate insulating film has:
• a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode;
• and a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that constitutes interfaces in combination with both the first insulating film and the semiconductor layer, the second insulating film being made of KNbO3, KTaO3, BaTiO3, CaSnO3, CaZrO3, CdSnO3, SrHfO3, SrSnO3, SrTiO3, YScO3, CaHfO3, MgCeO3, SrCeO3, BaCeO3, SrZrO3, BaZrO3, LiGaO2, mixed crystal (Li1−(x+y)NaxKy)(Ga1−zAlz)O2 of LiGaO2, or a solid solution having at least two of these oxides.