SEMICONDUCTOR DEVICE AND MANUFACTURE THEREOF

PROBLEM TO BE SOLVED: To prevent the depletion of a gate electrode by forming an N-well and a P-well on a silicon substrate, then forming an isolation region and a gate oxide film, further depositing polysilicon, and patterning a gate electrode with the polysilicon formed in a predetermined thickness. SOLUTION: A silicon oxide film 202 and silicon nitride film 203 are sequentially deposited on a silicon substrate 201 by thermal oxidation. Then, a photomask 204 is formed on an N-channel region, and phosphorus P for forming a well is implanted. Thereafter, an oxide film 205 is formed on a P- channel region, boron for forming well is implanted, and a LOCOS isolation region 207 and twin wells 206 of N-well, P-well are formed. Then, a gate oxide film 208 is formed, and then polysilicon 209 is deposited. The polysilicon 209 is formed in a predetermined thickness, flattened, and a gate electrode is patterned. Thus, the depletion of the gate electrode can be prevented.