consecutively forming a semiconductor layer and a multilayer metallic film to overlie a substrate, said multilayer metallic film including a high-melting-point metal (HMPM) film and a first metallic film having a lower resistivity than said HMPM film, wherein the first metallic film comprises an Al or Al-alloy film;

forming a photoresist mask on said multilayer metallic film;

patterning said multilayer metallic film by using said photoresist mask to form a multilayer metallic pattern, said patterning including a side etching for retracting edges of said multilayer metallic pattern beyond edges of line patterns of said photoresist mask;

forming a protection film after said patterning comprising at least one of Al oxide or Al hydroxide on exposed portions of said first metallic film by hot-water washing;

dry-etching at least a portion of said semiconductor layer after forming said protection film by using said photoresist mask as an etching mask; and

removing said photoresist mask,

wherein said patterning step includes wet etching.