US Patent 7250661 Semiconductor memory device with plural source/drain regions

A semiconductor memory device includes first and second source/drain regions, and first and second semiconductor regions. The first source/drain region of a first conductive type is formed in a first well region of a second conductive type for a pair of first MIS-type transistors of the first conductive type. The second source/drain region of the second conductive type is formed in a second well region of the first conductive type for a pair of second MIS-type transistors of the second conductive type. The first semiconductor region of the second conductive type is formed in the first source/drain region. The second semiconductor region of the first conductive type is formed in the second source/drain region.