Method for forming wiring in semiconductor device

A method for forming wiring in a semiconductor device, comprising the steps of:

• depositing a first insulating layer and a second insulating layer sequentially on the silicon substrate;
• exposing a predetermined part of the substrate by etching the first and second insulating layers;
• forming a trench by etching the exposed part of the substrate;
• forming a third insulating layer on the surface of the trench by thermal oxidation;
• depositing wiring materials to fill the trench;
• forming wiring in the lower part of the trench by etching back the wiring materials;
• forming a fourth insulating layer on the wiring;
• removing the third insulating layer on the fourth insulating layer;
• forming an epitaxial silicon layer so that the trench can be completely filled;
• forming a contact hole exposing the wiring by etching the epitaxial silicon layer and the fourth insulating layer;
• forming a fifth insulating layer at the side wall of the contact hole;
• removing the first and second insulating layers;
• forming a wiring plug in the contact hole in which the fifth insulating layer has been formed.