A vehicle headrest apparatus has a headrest unit mounted to an upper end of a seatback. Each sensor unit area is partitioned into two individual circuit areas. The carbon containing gas can be selected from gases having the general formula CxHy, such as, for example, CH4, C2H2, C2H4, and C2H6. The plurality of openings may include an elongate opening. No high frequency clock is required to produce subtle differences of charge ratio in negative polarity writing in which the resistances of the switching elements fall. In a method for manufacturing a semiconductor device including a thin film transistor in which a semiconductor layer including a channel formation region serves as an oxide semiconductor film, heat treatment for reducing impurities such as moisture is performed after an oxide insulating film serving as a protective film is formed in contact with an oxide semiconductor layer.