A method of making an electronic device comprising a double bank well-defining structure, which method comprises: providing an electronic substrate; depositing a first insulating material on the substrate to form a first insulating layer; depositing a second insulating material on the first insulating layer to form a second insulating layer; removing a portion of the second insulating layer to expose a portion of the first insulating layer and form a second well-defining bank; depositing a resist on the second insulating layer and on a portion of the exposed first insulating layer; removing the portion of the first insulating layer not covered by the resist, to expose a portion of the electronic substrate and form a first well-defining bank within the second well-defining bank; and removing the resist. The method can provide devices with reduced leakage currents.