Method for manufacturing array substrate, array substrate, and display device

A method for manufacturing an array substrate, comprising:

• forming a light-shielding layer and a buffer layer in sequence on a base substrate;
• forming an active layer on a side of the buffer layer facing away from the base substrate and forming a first via hole in the active layer;
• forming an interlayer dielectric layer on a side of the active layer facing away from the base substrate;
• forming a second via hole in the interlayer dielectric layer at a position corresponding to the first via hole and forming a third via hole in the buffer layer at a position corresponding to the first via hole by a single patterning process, wherein a critical dimension of the second via hole is greater than critical dimensions of the first via hole and the third via hole, and orthogonal projections of the first via hole and the third via hole on the base substrate fall into a range of an orthogonal projection of the second via hole on the base substrate;
• and
• forming a source/drain electrode layer on a side of the interlayer dielectric layer facing away from the base substrate, wherein the source/drain electrode layer is electrically connected to the light-shielding layer through the second via hole, the first via hole and the third via hole in sequence.