Method of manufacturing a transistor in a semiconductor device

A method of manufacturing a transistor in a semiconductor device, comprising the steps of:

• injecting each of first impurity and second impurity into given regions of a semiconductor substrate to define a first region and a second region;
• forming a gate insulating film on said semiconductor substrate in which said first region and said second region are defined;
• forming a first Ta film having a first nitrogen composition on said first region so that the first Ta film has a first work function;
• forming a second Ta film having a second nitrogen composition on said second region so that the second Ta film has a second work function;
• forming a metal layer on the entire structure including said first and second TaNx films;
• patterning said metal layer, said first and second TaNx films, and said gate insulating film to form gate electrodes in said first and second regions, respectively;
• and
• forming a first junction region by injecting the first impurity into said semiconductor substrate in said first region and forming a second junction region by injecting the second impurity into said semiconductor substrate in said second region,
• wherein said first work function of said first Ta film is smaller than said second work function of said second Ta film, and said first and second Ta films are formed using one of TaCl3, Ta(OC2H5)4, TDMAT and TDEAT as a Ta precursor and using one of NH3, N2 and ND3 as a nitrogen source.