Semiconductor device including IGZO layer and manufacturing method thereof

A method for manufacturing a semiconductor device comprising the steps of:

• introducing a substrate into a chamber, wherein the chamber is provided with a target comprising In, Ga and Zn, and wherein a relative density of the target is greater than or equal to 80%;
• forming an oxide semiconductor layer by sputtering over the substrate, wherein the substrate is heated during the sputtering;
• removing moisture by using a cryopump from the chamber during forming the oxide semiconductor layer by sputtering;
• and
• performing dehydration or dehydrogenation by heat treatment after the oxide semiconductor layer is formed,
• wherein the oxide semiconductor layer comprises In, Ga and Zn, and
• wherein a purity of an inert gas which is introduced into a heat treatment apparatus during the heat treatment is set greater than or equal to 99.9999%.