Abstract: A method of forming a contact hole in a semiconductor device, by which a PMD layer as an insulating interlayer is prevented from being overetched by wet cleaning for removing polymer and photoresist after forming a contact hole perforating the PMD layer in a manner of adjusting temperature and concentration of an NC-2 solution for the wet cleaning. The present invention includes the steps of forming a premetal dielectric layer on a semiconductor substrate, forming a contact hole perforating the premetal dielectric layer, and cleaning the substrate using an NC-2 cleaning solution at a temperature equal to or lower than about 55° C.