| 摘要 |
PURPOSE:To control the threshold voltage of an MOS semiconductor device by preselecting the densities of source and drain regions in response to the predetermined width of a gate to be formed and diffusing them. CONSTITUTION:When the width of a gate is small and the threshold voltage is controlled by the short channel effect of the actual channel length (L) instead of the inversion of the semiconductor substrate, the real channel length L is given by L=W-2xj, where W represents the width of the gate, xj represents the diffusion depth to the semiconductor substrate, which depends upon the diffusion impurity density to increase with the increase of the impurity density under a predetermined heat treatment. Accordingly, the desired threshold voltage can be controlled by controlling the diffusion impurity density. Therefore, a diagram in which the width of the gate and the threshold voltage vs. impurity density of the source and drain regions is prepared on the basis of the measurements, and the diffusion density is selected in response to the width of the gate. |
