Patent ID: 8163148

Claim:
A gas sensor element comprising: a sensor layer in which at least one pair of electrodes are provided in a solid electrolyte for measuring an electromotive force based on a difference in an oxygen concentration between atmospheres; and a heater layer which includes a heater element with a heat generating portion and an electrically insulating layer disposed so as to enclose the heater element and which is configured to heat, by an electric current supplied to the heater element, at least a portion of the solid electrolyte at which the at least one pair of electrodes are provided, the sensor layer and the heater layer being laminated integrally on each other, wherein the electrically insulating layer contains at least one metal oxide selected from the group consisting of alkali metal oxide and alkaline earth metal oxide, wherein at least one electrode of the at least one pair of electrodes has a tunnel-like structure comprising a ceiling electrode portion, lateral electrode portions and a bottom electrode portion in a space in the gas sensor element, and wherein an alkali metal oxide is contained in the electrically insulating layer in a total content of 2.5-5 wt %.