Patent ID: 6600205
Filing Date: 2003-07-29
Classification: H01L

Abstract:
A process for making a first, second, and third different types of MOS transistors in respective first, second and third regions of a semiconductor substrate comprising:a. forming a first well in the first region by implanting ions of a first certain species, energy and dosage in the first regions, the first well having a first certain depth and sheet resistance; b. forming a second well in the second region by implanting ions of a second certain species, energy, and dosage in the second region that is different from the first certain energy and dosage, the second well having a second certain depth and sheet resistance that is different from the first certain depth and sheet resistance; c. forming a third well in the third region by implanting ions in the third region of the first certain species, energy, and dosage at the time of the forming of the first well and by implanting ions in the third region of the second certain species, energy, and dosage at the time of the forming of the second well, the implanted ions in the third well including the sum of the implanted ions in the first and the second wells, the third well having a third certain depth and sheet resistance that is different from the first and the second certain depths and sheet resistances; d. forming a first type of an MOS transistor in the first well, the first well being the body and the channel region of the first type of MOS transistor; e. forming a second type of an MOS transistor in the second well, the second well being the body and the channel region of the second type of MOS transistor; and f. forming a third type of an MOS transistor in the third well, the third well being the body and the channel region of the third type of MOS transistor.