In a method for producing a gate structure for a MOS transistor, first, a layer sequence of oxide layer, auxiliary layer and masking layer is generated on a substrate, wherein the auxiliary layer and the masking layer are patterned to determine an edge separating an area of the oxide layer covered by these layers from an exposed area thereof. The sheets are transported by contacting upper and lower conveying elements of at least one upper and one lower conveying device, at least one of which is connected to a drive. The tube serves as a conduit for blood flow in an aneurysm of an aorta.