The present invention relates to a device (100) for depositing a layer based on polycrystalline silicon onto a substantially plane, elongate, moving support (4) having two longitudinal faces (43, 44) and two longitudinal side edges (41, 42), the device comprising: a crucible (1) containing a bath (2) of molten silicon, said support (4) being designed to be dipped at least in part in the bath and to pass substantially vertically in its long direction through the equilibrium surface (21) of the bath; and at least one edge control element (5, 5′), each edge control element being maintained substantially vertically close to one of the two longitudinal side edges (41, 42); each edge control element comprising walls (51 to 53′) defining a longitudinal slot (54, 54′) beside the corresponding longitudinal side edge, each slot being dipped in part in the bath (2) so as to raise the level of the bath by capillarity in the vicinity of the corresponding longitudinal side edge, the device being characterized in that at least one of the walls (51 to 52′), referred to as an “insertion” wall, facing part of one of the longitudinal faces, is substantially plane.