As the application of oxide semiconductor thin-film transistors (oxide TFTs) expands, higher electrical properties are required. Hydrogen (H) is a crucial element related to both the mobility and stability of oxide TFTs. Appropriate H incorporation induces enhanced characteristics; however, excessive H degrades TFTs. In this letter, we suggest inserting an interfacial layer (IL) deposited via plasma-enhanced atomic layer deposition of several cycles to control H at the atomic-scale. As the number of IL deposition cycles increase from 0 to 10 cy, both mobility and stability improve. Furthermore, TFT with IL of 15 cy lost its on/off characteristic. Considering the analysis results, it was confirmed that the control of H concentration through IL can effectively improve the electrical characteristics of oxide TFTs. The oxide TFT with IL of 10 cy and optimized incorporation of H exhibits a high mobility of 50.12 cm(2)/V.s with great stability.