Method of manufacturing semiconductor device having triple-well structure and semiconductor device fabricated

A method for fabricating semiconductor device having a plurality of well structures including a triple-well structure, comprising the steps of:

• forming a first resist film having an opening at a position corresponding to a first well forming area on a fist conductivity type substrate;
• implanting second conductivity type impurity into the first well forming area by masking with the first resist film;
• removing the first resist film;
• forming a first well having a second conductivity type well by diffusing and activating the second conductivity type impurity implanted into the first well forming area with a heating process;
• forming a neutering resist mask having openings at a position corresponding to at least two of the first well forming areas in the first conductivity type well;
• implanting additional impurity of the second conductivity type into the first well forming area by masking with the neutering resist mask and the first resist film;
• removing the neutering resist mask;
• forming a second resist film having openings at a position corresponding to a second well forming area in the first well and at a position corresponding to a third well forming area which is located in an area other than the first well forming area on the substrate;
• implanting first conductivity type impurity into the second and third well forming areas by masking with the second resist film;
• removing the second resist film;
• forming a third resist film having openings at a position corresponding to a fourth well forming area in the first well and a position corresponding to a fifth well forming area which is located in an area other than the first well forming area on the substrate, the fourth and fifth well forming areas being areas where the first conductivity type impurity is not implanted;
• implanting additional impurity of the first conductivity type into the fourth and fifth well forming areas by masking with the third resist film;
• removing the third resist film;
• and
• forming a second well and a fourth well in the first well forming area and a third well and a fifth well in an area other than the first well forming area by diffusing and activating the first conductivity type impurity implanted into the first well forming area with a heating process.