Semiconductor apparatus with improved ESD withstanding voltage

A semiconductor apparatus formed on a semiconductor substrate having a first conductivity type, comprising:

• an internal circuit in the central portion of said semiconductor substrate;
• a plurality of external connection terminals formed in a first portion of said semiconductor substrate around said internal circuit, each external connection terminal being electrically connected to said internal circuit, wherein a plurality of power supplies correspondingly supply different voltage levels to the plurality of external connection terminals;
• and
• a plurality of outer ESD protective circuits formed in a second portion of said semiconductor substrate or a common well region in said semiconductor substrate, around said first portion of said semiconductor substrate;
• wherein each of said outer ESD protective circuits further comprises
• a first diffusion region electrically connected to one of the external connection terminals,
• a second diffusion region formed separately from said first diffusion region, said second diffusion region being electrically connected to a higher voltage line of a main power supply, and
• a third diffusion region formed separately from said first diffusion region, at a side of said first diffusion region opposite from said second diffusion region, said third diffusion region being electrically connected to a lower voltage line of said main power supply.