Effects of oxygen gas in the sputtering process of the WO3 sensing layer on NO2 sensing characteristics of the FET-type gas sensor

•NO2 gas sensing characteristics of the FET-type sensor with WO3 sensing layer are analyzed.•A WO3 sensing layer is deposited by using the DC magnetron sputtering method.•NO2 sensing characteristics of the gas sensors with the WO3 sensing layer deposited under three different sputtering conditions are compared.•As the ratio of oxygen gas in the total sputtering gas increases, the response of the gas sensor increases since the size of the grain is reduced at the grain boundary increases.