| 摘要 |
PURPOSE:To enable the control of the threshold voltage value of a transistor by a method wherein an impurity profile that the impurity concentration becomes higher in the neighborhood of the center of an impurity layer viewed in the depth direction, and lower in the surface of a well is obtained by a heat processing at low temperature. CONSTITUTION:A thick Si oxide film 22 is formed on a semiconductor substrate 21, and, using the technique of photoetching, other parts are removed by leaving only element isolation regions. Semiconductor epitaxial films 23 are selectively formed only on the exposed semiconductor layer of the substrate up to the surface of the oxide film 22. Ions are implanted with a resist as a mask, and thereafter an N type impurity layer or a P type impurity layer 24 is formed by the heat processing low temperature. Then, the lateral spread of the impurity layer is blocked by the oxide film, and the distance required for the element isolation of channel devices 25 and 26 becomes smaller. Therefore, the control of the threshold voltage value of the transistor is enabled. |
