Thin-film transistor circuit and method of manufacturing thin-film transistor circuit

A circuit comprising:

• a polysilicon thin-film transistor comprising:
• a polysilicon layer;
• a first conductor layer located above the polysilicon layer;
• a first insulator layer located between the first conductor layer and the polysilicon layer;
• and
• an oxide semiconductor thin-film transistor comprising:
• an oxide semiconductor layer;
• a second conductor layer located above the oxide semiconductor layer;
• and
• a second insulator layer located between the second conductor layer and the oxide semiconductor layer,
• wherein the polysilicon layer includes a polysilicon part of the polysilicon thin-film transistor,
• wherein the first conductor layer includes a first gate electrode part of the polysilicon thin-film transistor,
• wherein the first insulator layer includes a first insulator part located between the first gate electrode part and the polysilicon part,
• wherein the oxide semiconductor layer includes an oxide semiconductor part of the oxide semiconductor thin-film transistor,
• wherein the second conductor layer includes a second gate electrode part of the oxide semiconductor thin-film transistor,
• wherein the second insulator layer includes a second insulator part located between the second gate electrode part and the oxide semiconductor part,
• wherein the second insulator layer has a relative permittivity of not less than 8,
• wherein the entire area of the second insulator layer is covered with the second conductor layer,
• wherein the oxide semiconductor part includes a channel region and source/drain regions sandwiching the channel region, and
• wherein the oxide semiconductor thin-film transistor includes compound interfacial parts each located above a source/drain region, the compound interfacial parts including constituent elements of the oxide semiconductor part and constituent elements of the second insulator layer and having a resistance lower than a resistance of the channel region,
• wherein the second conductor layer of the oxide semiconductor thin-film transistor is above of the upper electrode part of a capacitive element,
• wherein the second insulator layer of the oxide semiconductor thin-film transistor is above of the insulator part of the capacitive element.

A method of manufacturing a circuit, the method comprising:

• forming a polysilicon thin-film transistor, wherein the forming the polysilicon thin-film transistor comprises:
• forming a polysilicon layer including a polysilicon part of the polysilicon thin-film transistor;
• forming a first insulator layer including an insulator part of the polysilicon thin-film transistor on a layer above the polysilicon layer;
• forming a first conductor layer including a gate electrode part of the polysilicon thin-film transistor on a layer than above the first insulator layer;
• and
• forming an oxide semiconductor thin-film transistor, wherein the forming the oxide semiconductor thin-film transistor comprises:
• forming an oxide semiconductor layer including an oxide semiconductor part of the oxide semiconductor thin-film transistor;
• forming a second insulator layer including an insulator part of the oxide semiconductor thin-film transistor on a layer above the oxide semiconductor layer;
• and
• forming a second conductor layer including a gate electrode part of the oxide semiconductor thin-film transistor on a layer above the second insulator layer,
• wherein the second insulator layer has a relative permittivity of not less than 8, and
• wherein the second conductor layer and the second insulator layer are etched together or the second insulator layer is etched using the second conductor layer as a mask,
• wherein the first insulator layer has a relative permittivity lower than the relative permittivity of the second insulator layer,
• wherein the second conductor layer includes an upper electrode part of a capacitive element, and
• wherein the second insulator layer includes an insulator part of the capacitive element,
• wherein the second conductor layer of the oxide semiconductor thin-film transistor is above of the upper electrode part of the capacitive element,
• wherein the second insulator layer of the oxide semiconductor thin-film transistor is above of the insulator part of the capacitive element.