Semiconductor integrated circuit memory

Abstract

A semiconductor integrated circuit memory is disclosed in which a first impurity-doped layer for making circuit elements such as MESFET's and a second impurity-doped layer opposite in conductivity type to the first impurity-doped layer are formed in a semi-insulating substrate in such a manner that the second impurity-doped layer is formed under and between circuit elements for making up a memory cell array part and a peripheral circuit part, and is divided into at least first and second regions. For example, the first region formed under and between the circuit elements of the memory cell array part is made of a P-type layer which is high in carrier density, and the second region formed under and between the circuit elements of the peripheral circuit part is made of a P-type layer which is low in carrier density. The high carrier-density P-type layer formed under the memory cell array part allows a memory cell having a minimum critical charge for alpha-particles to gain satisfactory alpha-particle immunity even when the memory cell is made fine in size. Further, the low carrier-density P-type layer formed under the peripheral circuit part having a critical charge larger than that of the memory cell can improve the alpha-particle immunity of the peripheral circuit part and can suppress an increase in parasitic capacitance at the peripheral circuit part to maintain the high-speed operation of the memory.