METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE USING POLYSILICON-GERMANIUM AS GATE ELECTRODE

摘要

PURPOSE: A method for manufacturing a semiconductor device using polysilicon-germanium as a gate electrode is provided to improve surface roughness of the gate electrode, by forming the gate electrode composed of a lower polysilicon layer, a polysilicon-germanium layer and an upper polysilicon layer while germanium content maintains 20 percent. CONSTITUTION: A gate oxide layer(2), a lower polysilicon layer(3) and a polysilicon-germanium layer are sequentially deposited on a semiconductor substrate(1). A polysilicon layer of a predetermined thickness is formed on the polysilicon-germanium layer. The resultant structure is patterned to form a gate electrode. A lightly-doped-drain(LDD) oxide layer(6) is deposited on the resultant structure having the gate electrode, and low density ions are implanted. After a spacer(8) is formed on the LDD oxide layer, high density ions are implanted into a source/drain region. Germanium ions are activated to form a conductive layer(10) for a gate of polysilicon-germanium on the polysilicon layer by a heat treatment process.