Etching agent, etching method and etching agent formulation

An objective of this invention is to provide an etching agent and an etching method for titanium-based metal on semiconductor substrate and an etching agent formulation for being mixed with hydrogen peroxide to be used, which are capable of suppressing decomposition of hydrogen peroxide, and has having a long liquid lifetime and less requirement of hydrogen peroxide concentration control in the etching agent, even for the application to the semiconductor substrate having a titanium-base metal and a cupper metal or a cupper alloy. The present invention is directed to an etching agent for titanium-based metal on a semiconductor substrate having a titanium-based metal, and a metal cupper or a cupper alloy over the titanium-based metal; an etching method using the etching agent, and an etching agent formulation for being mixed with hydrogen peroxide to be used. The etching agent is characterized by comprising an aqueous solution at least comprising (A) a hydrogen peroxide, (B) a phosphonic acid chelating agent ha