US Patent 7471545 Semiconductor memory device

Source contacts of driver transistors are short-circuited through the use of an internal metal line within a memory cell. This metal line is isolated from memory cells in an adjacent column and extends in a zigzag form in a direction of the columns of memory cells. Individual lines for transmitting the source voltage of driver transistors can be provided for each column, and the source voltage of driver transistors can be adjusted also in units of memory cell columns in the structure of single port memory cell.