The physical properties of amorphous In-Ga-Zn-O (a-IGZO) films deposited by DC sputtering with various sputtering pressure were investigated. In accordance with improvement of the transistor performances such as saturation mobility (μSAT) and sub-threshold swing with a lowering the sputter pressure, we found that the sputtering pressure affected various physical properties of a-IGZO film. The lower sputtering pressure caused a film densification, a decreasing the surface roughness and small hydrogen concentration in the films.