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

A method of manufacturing a thin-film transistor substrate, comprising:

• forming a polysilicon film on an insulating substrate as an active film of a first thin-film transistor;
• forming an oxide semiconductor film on a layer upper than the polysilicon film on the insulating substrate as an active film of a second thin-film transistor after forming the polysilicon film;
• forming a first insulating film on a layer upper than the oxide semiconductor film after forming the oxide semiconductor film;
• and
• forming a second insulating film on a layer upper than the first insulating film after forming the first insulating film, the second insulating film containing hydrogen at a concentration higher than a concentration of hydrogen in the first insulating film,
• wherein the first insulating film is in contact with the oxide semiconductor film and covers at least a part of the polysilicon film and at least a part of the oxide semiconductor film when viewed planarly,
• wherein the first insulating film includes a first part and a second part,
• wherein the first part includes a part covering the at least a part of the polysilicon film,
• wherein the second part includes a part covering the at least a part of the oxide semiconductor film,
• wherein the second insulating film covers the at least a part of the polysilicon film and the at least a part of the oxide semiconductor film when viewed planarly, and
• wherein the forming the first insulating film includes etching the first insulating film to make the first part thinner than the second part.