Etching liquid, etching method using same, and method for manufacturing semiconductor element

An etching liquid for processing a substrate that has a first layer containing titanium nitride (TiN) and a second layer containing at least one metal that is selected from among group 3-11 transition metals, which selectively removes the first layer. This etching liquid contains an inorganic compound that is represented by formula (1), an oxidant, and an anti-corrosion agent for the second layer. Hal-Q (1) (In the formula, Hal represents a halogen atom, and Q represents an atom or an atomic group that forms a monovalent cation.)