In a micromechanical sensor (11) for measuring a mass flow rate in accordance with the Coriolis principle, two line sections (13) are mounted in a suspension means (24) such that they can oscillate, as a result of which they can be caused to oscillate in phase opposition (essential for the measuring principle). A spacer layer (18) is provided between the layers (12a, 12b) forming the line sections (13), the spacer layer ensuring that there is a space between the line sections (13) in the quiescent state. Oscillation of the line sections in phase opposition only becomes possible at all as a result of this since this prevents collision of the line sections (13) as they approach one another.