A thermal flow sensor has a first, second and third substrate, each having a first side and a second opposite side. The first substrate is connected to the second substrate such that the second side of the first substrate abuts the first side of the second substrate. The third substrate is connected to the second substrate such that the second side of the second substrate abuts the first side of the third substrate. The first, second and third substrate form a multi-layer body structure having at least one edge extending between a first side of the first substrate and the second side of the third substrate. The second substrate has a groove formed therein so as to form a conduit bounded by the second substrate and the second side of the first substrate and the first side of the third substrate. The conduit has an inlet opening and an outlet opening that are formed in the at least one edge.
