| 摘要 |
PURPOSE: To reduce a capacitance between mutual connection and a substrate by using a buried layer that is lightly doped between the mutual connection and the substrate. CONSTITUTION: A buried layer 14 (LDBL) that is lightly doped is provided at the lower side of an oxide 6 and extends horizontally from a mutual connection 2. The LDBL is lightly doped by a dopant substance with a conductivity type that is opposite to that of a substrate 8. For example, the substrate is of a P-type, and the LDBL is doped with an N-type substance. The thickness of LDBL is limited to a value that is equal to or less than the thickness of an adjacent P+-channel strip. Therefore, a depleted region is formed together with a related capacitance, and an additional capacity operates in series with an oxide capacitance Cg. The entire capacitance of the two elements that operate in series is inversely proportional to the sum of the inverse number of the two capacitances, thus reducing the entire capacitance by adding an LDBL capacity. |
