Semiconductor device and manufacturing method thereof

摘要

Junction leakage in a medium voltage MOS transistor having a silicide structure is prevented. A titanium layer is formed by sputtering titanium over the entire surface of a semiconductor substrate. A gate electrode makes contact with the titanium layer through an opening and P⁺-type diffusion layers make contact with the titanium layer through openings. In subsequent heat treatment, portions of the titanium layer contacting the gate electrode or each of the P⁺-type diffusion layers are changed into silicide, forming titanium silicide layers on the gate electrode and the P⁺-type diffusion layers. Then the rest of the titanium layer, which is on the silicide block layer and not changed into silicide, is removed by wet-etching.