Gas sensor and method for manufacturing the gas sensor

摘要

It is an object to provide a gas sensor which is formed by a simple manufacturing process. Another object is to provide a gas sensor whose manufacturing cost is reduced. A transistor which includes an oxide semiconductor layer in contact with a gas and which serves as a detector element of a gas sensor, and a transistor which includes an oxide semiconductor layer in contact with a film having a gas barrier property and which forms a detection circuit are formed over one substrate by the same process, whereby a gas sensor using these transistors may be formed.

主权项

1. A method for manufacturing a gas sensor having a detection portion and a circuit portion, the method comprising the steps of:
forming a first gate electrode layer and a second gate electrode layer over an insulating surface; forming a gate insulating layer over the first gate electrode layer and the second gate electrode layer; forming a first oxide semiconductor layer and a second oxide semiconductor layer over the gate insulating layer; and forming a protective insulating layer comprising an oxide insulating film and a silicon nitride film over the second oxide semiconductor layer, the oxide insulating film being in contact with an exposed portion of the second oxide semiconductor layer, wherein the first gate electrode layer and the first oxide semiconductor layer are formed in the detection portion, and wherein the second gate electrode layer, the second oxide semiconductor layer, and the protective insulating layer are formed in the circuit portion.