Removal of a sulfur atom from the topmost layer of a MoS2 surface forms electronic states in the band-gap of an inherently semiconducting material. Scanning tunneling spectroscopy measured at sulfur vacancies, which were made by sulfur atom removal using the high electrical field of a scanning tunneling microscope, shows stepwise increases in the current in a band-gap region, corresponding to the formation of electronic states. The periphery of sulfur vacancies also show linear current-voltage (I/V) characteristics, suggesting that electronic states in the periphery are modified due to the removal of sulfur atoms. (C) 2012 The Japan Society of Applied Physics