[en] We introduce single-phase In-Ge-Sb-Te (IGST) quaternary thin film (fcc structure when crystallized) deposited by cosputtering from Ge₂Sb₂Te₅(GST) and In₃Sb₁Te₂ targets. This film, compared with the GST ternary system, provides a significant increase of amorphous-to-crystalline transformation temperature. High-resolution x-ray photoelectron spectroscopy (HRXPS) revealed that, with increasing In amounts, the Sb 4d and Ge 3d core peaks shift toward lower binding energies (BEs), with negligible changes in spectral linewidths, whereas the In 4d and Te 4d core peaks show insignificant changes in BEs. HRXPS interpretation suggests that the Na site in IGST can be occupied by Te, Sb, In, and vacancy, whereas in GST it is occupied only by Te