| 摘要 |
PROBLEM TO BE SOLVED: To reduce the undershoot noise and realize a high speed and low power consumption by providing second p-wells which are separated by an n-type diffusion layer from a p-type substrate and held at the ground potential and n-channel transistors of input/output circuits provided in these wells. SOLUTION: On a p-type substrate 101 fixed to a negative potential Vbb, first p-wells 103 connected to this substrate 101 in which central transistors 106 and n-channel transistors 105 of peripheral circuits are disposed. Second p-wells 102 are surrounded with n-wells 108 and n-type deep diffused layer 107 at the side and below and electrically isolated from the substrate 101 in which n-channel transistors 104 of input/output circuits are disposed. The second p-wells 102 are fixed to the ground potential, unlike the p-type substrate 101. If, hence the undershoot enters from an output circuit to inject electrons in the second p-wells 102, they will be absorbed by the n-type diffused layer 107. |
