The invention relates to a flow sensor (1), comprising: a semiconductor module (2) on which a temperature sensing means (13a, 13b) and a heat source (12) are arranged, a flow channel (6) for guiding the fluid medium in a flow direction (D), and a wall (W) delimiting the flow channel, wherein said heat source (12) and said temperature sensing means (13a, 13b) are configured such that they are in thermal contact with said wall (W). According to the invention, said wall (W) comprises a glass member (4) and a metal member (3a), wherein the glass member (4) is connected to the metal member (3a).