PURPOSE: To reduce the number of manufacturing processes by a method wherein a polyimide resin film as a final protective film is formed in a process prior to formation of an metal protrusion electrode and the film is used as a gap film during a lift-off operation of a second metal film and as a mask during a metal plating operation.

CONSTITUTION: Gold protrusion electrode formation regions 4A and a wiring part is for plating use which connects these regions are formed; after that, a photoresist film 5 is removed; then, a polyimide resin film 6 is formed on the whole surface by a spin coating method. Then, the polyimide resin film 6 on the gold protrusion electrode formation regions 4A is removed by using the patterned photoresist film 5A. Then, titanium and platinum are applied continuously to the whole surface including the photoresist film 5A; a titanium- platinum film 8 is formed. Then, the photoresist film 5A and the titanium- platinum film 8 formed on it are removed by a lift-off method. Then, only the surface of a silicon substrate 1 is immersed in a gold plating liquid and is plated with gold; a gold protrusion electrode 9 is formed on the titanium- platinum film 8.