Semiconductor device having pocket and manufacture thereof

A method of manufacturing a semiconductor device comprising the steps of:

• (a) forming an isolation region in a silicon substrate having a principal surface to define first and second active regions;
• (b) forming a gate insulating film in the first and second active regions;
• (c) forming a conductive gate electrode layer on the gate insulating film;
• (d) pattering the gate electrode layer and the gate insulating film to form a first insulated gate on the first active region and a second insulated gate on the second active region;
• (e) implanting n-type impurity ions into the first and second active regions to a first depth to form first and second extension regions on both sides of each of the first and second insulated gates;
• (f) masking the second active region and implanting indium ions at a first dose into the first active region to a second depth deeper than the first depth;
• and
• (g) masking the first active region and implanting indium ions at a second dose smaller than the first dose into the second active region to a third depth deeper than the first depth.