Metal etching method and semiconductor device

The invention provides a metal etching method and a semiconductor device. The method comprises the steps that firstly, a substrate is provided, and the substrate comprises a substrate body, a first isolation layer, a metal layer and a second isolation layer which are stacked in sequence; and then, part of the second isolation layer, part of the metal layer and part of the first isolation layer are removed, so that part of the first isolation layer is exposed, a groove and a polymer layer located on the side wall of the groove are formed, and etching gas adopted for removing part of the metal layer at least comprises one of ethylene and methane. According to the method, ethylene or methane is added into the etching gas, the ethylene or methane can be subjected to a polymerization reaction with the photoresist at high temperature and high pressure to generate a polymer, and the polymer attached to the side wall of the groove can prevent the side wall of the groove from being eroded in the etching process to cau