An intermittent etching process for forming efficiently by reactive ion etching (RIE), a minute recess, such as a groove having an opening width as small as about 0.1 .mu.m, with a large aspect ratio in layers of metals, semiconductors, etc. The process comprises alternating RIE steps of brief duration e.g. 30 seconds with vacuumizing for evacuating gaseous reaction products produced in the RIE step from the etched recess. The process is particularly suitable for formation of a bridging portion of Nb, etc. constituting Josephson devices, by making use of three layered resist technique.