| 摘要 |
PURPOSE:To improve the controllability of a threshold voltage value, by forming a P-base and an N<+> source with a nitride film as a mask, thereafter removing the nitride film, and implanting ions in the entire surface or in only a part of the place, where the nitride film has been located. CONSTITUTION:On a semiconductor substrate 1, an oxide film 2 and a nitride film 3 are grown. Patterning is performed by a photolithography technology using resist 4. Thereafter, with the nitride film 3 as a mask, an impurity region 5, whose conductivity type is reverse with respect to that of the semiconductor substrate and an impurity region 6 having the same conductivity as that of the semiconductor substrate are formed. At a part beneath the nitride film 3, which is oxidized with the nitride film 3 as a mask, an oxide film is not grown. Therefore, a recess shape (bird's beak) is formed. Then, the nitride film 3 is removed. An impurity region 15, whose conductivity is reverse with respect to the substrate is formed on the entire part or a part of the place, where the nitride film has been located. Then, a gate electrode 8, a source elecrtrode 13 and a drain electrode 11 are formed sequentially, and a vertical type field effect transistor is formed. Since the threshold voltage value can be determined by the impurity region 15, control accuracy is improved. |
