Method of producing semiconductor device

A method of producing a semiconductor device having a first region including a first conductivity type MOS transistor, a second region including a second conductivity type MOS transistor, and first and second connecting sections for potential fixture which are respectively formed at a part of said first region and a part of said second region, said method comprising the following steps:

• providing a first resist mask over the first connecting section of said first region and said second region of said semiconductor substrate, said first resist mask being formed with a first opening portion to allow the second connecting section of said second region;
• forming an impurity diffusion layer other than source and drain regions in said first region by an oblique ion implantation of impurity ion into a surface of said semiconductor substrate at an implantation angle to prevent the impurity ion from reaching a bottom surface of said first opening portion upon using a first resist mask;
• forming the source and drain regions in said first region and the second connecting section in said second region by substantially vertically ion-implanting impurity ion to said semiconductor substrate by using said first resist mask;
• removing said first resist mask;
• forming a second resist mask over the second connecting section in said second region and said first region, said second resist mask being formed with a second opening:
• portion to expose a part where the first connecting section of said first region is to be formed;
• forming an impurity diffusion layer other than source and drain regions in said second region by an oblique ion implantation of impurity ion into the surface of said semiconductor substrate at an implantation angle to prevent the impurity ion from reaching a bottom surface of said second opening portion by using said second resist mask;
• and
• forming source and drain regions in said second region and a first connecting section in said first region by substantially vertically ion-implanting impurity into the surface of said semiconductor substrate by using said second mask.