Micromachining treatment agent and micromachining treatment method

Provided are a micromachining treatment agent and a micromachining treatment method with which it is possible to selectively perform micromachining on a silicon oxide film when performing micromachining on a laminated film comprising at least a silicon nitride film, a silicon oxide film, and a silicon alloy film. This micromachining treatment agent is used for micromachining a laminated film comprising at least a silicon oxide film, a silicon nitride film, and a silicon alloy film. The present invention relates to a water-soluble fluorine-containing resin composition which contains (a) 0.01-50 mass% of hydrogen fluoride, (b) 0.1-40 mass% of ammonium fluoride, (c) 0.001-10 mass% of a water-soluble polymer, (d) 0.001-1 mass% of an organic compound having a carboxyl group, and (e) water as any component, and which is characterized in that: the water-soluble fluorine-containing resin composition contains (a) 0.01-50 mass% of hydrogen fluoride; (b) 0.1-40 mass% of ammonium fluoride; (c) 0.001-10 mass% of a water-s