Sensor element, method of manufacturing a sensor element, and gas sensor

A method for manufacturing a sensor element, said sensor element comprising a first solid electrolyte layer having a first through hole which penetrates from a first obverse surface to a first reverse surface located on a side opposite the first obverse surface and a second solid electrolyte layer having a second through hole which penetrates from a second obverse surface to a second reverse surface located on a side opposite the second obverse surface and which connects to overlaps the first through hole in a penetrating direction, the second solid electrolyte layer being stacked on the first solid electrolyte layer by bringing the first reverse surface and the second obverse surface into contact with one another directly or through another member, the first solid electrolyte layer comprising a first inner insulating layer provided on an inner surface of the first through hole, a first outer insulating layer connected to the first inner insulating layer and provided on the first reverse surface, a first inner conductive layer provided on the first inner insulating layer, and a first outer conductive layer directly connected to the first inner conductive layer and provided on the first outer insulating layer, the second solid electrolyte layer comprising a second inner insulating layer provided on an inner surface of the second through hole, a second outer insulating layer connected to the second inner insulating layer and provided on the second obverse surface, a second inner conductive layer provided on the second inner insulating layer, and a second outer conductive layer directly connected to the second inner conductive layer and provided on the second outer insulating layer, and wherein the first outer conductive layer and the second outer conductive layer are in direct contact with one another and overlap one another in the penetrating direction, the method comprising:

• forming an insulating layer which comprises forming said first inner insulating layer on an inner surface of the first through hole of the first solid electrolyte layer before stacking, forming on the first reverse surface said first outer insulating layer which is connected to the first inner insulating layer, forming said second inner insulating layer on an inner surface of the second through hole of the second solid electrolyte layer, and forming said second outer insulating layer which is connected to the second inner insulating layer on the second obverse surface;
• forming said conductive layer which comprises forming said first inner conductive layer on the first inner insulating layer, forming on the first outer insulating layer said first outer conductive layer which is connected to the first inner conductive layer forming said second inner conductive layer on the second inner insulating layer, and forming on the second outer insulating layer said second outer conductive layer which is connected to the second inner conductive layer;
• and
• stacking the first solid electrolyte layer and the second solid electrolyte layer while the first outer conductive layer and the second outer conductive layer are brought into direct contact with one another.