C doped (1.5 wt.%) GST (CGST) thin film was formed on Si substrate by using sputter method with 100 nm-thick and confirmed resistance, atomic structure, and chemical state of CGST. From exploring chemical states of amorphous and crystalline CGST, we found the C-C bonding with cluster structure/Ge-C bonding and the deep double bonding (Ge=C) in amorphous and crystalline phases, respectively. The reverse-relationship between Ge-C and Ge=C bonds in amorphous and crystalline phases is observed in the analysis of chemical states.