Refrigerator and control method therefor

An ice maker comprising:

• a tray configured to form at least a portion of a cell that is a space in which a liquid is phase-changed into ice;
• and
• a tray cover coupled to the tray,
• wherein the tray includes a first portion that defines at least a portion of the cell and a second portion extended from a predetermined point of the first portion,
• wherein the second portion includes a first extension part extending from a first point of the first portion and a second extension part extending from a second point of the first portion,
• wherein the tray cover includes:
• a first wall having a portion provided to surround the first extension part, and
• a second wall having a portion provided to surround the second extension part, and
• wherein a first height of the portion of the first wall is different from a second height of the portion of the second wall.