Thin film semiconductor device and organic light-emitting display apparatus

A thin film semiconductor device comprising:

• a substrate;
• an active pattern on the substrate and comprising a rounded upper edge portion and a rounded lower edge portion;
• a first buffer film on the substrate;
• and
• a second buffer film on the first buffer film and contacting a flat lower surface of the active pattern without contacting the rounded lower edge portion of the active pattern.

An organic light-emitting display apparatus comprising:

• a substrate;
• a plurality of thin film transistors on the substrate;
• a pixel electrode electrically connected to one of the plurality of thin film transistors;
• an opposed electrode on the pixel electrode;
• and
• an interlayer between the pixel electrode and the opposed electrode, and comprising an organic light-emitting layer,
• wherein the at least one of the plurality of thin film transistors further comprises:
• an active pattern on the substrate and comprising a rounded upper edge portion;
• a first gate insulation film exposing the rounded upper edge portion and covering a flat portion of an upper surface of the active pattern;
• a second gate insulation film covering the rounded upper edge portion and the first gate insulation film;
• and
• a gate electrode on the first gate insulation film and the second gate insulation film, and overlapping part of the active pattern.