After automatic cell placement, the following steps are performed before performing
automatic inter-cell routing. (S22) Estimated wires having Manhattan-length
path are connected between same-node terminals of cells, and detected and counted
is a crosstalk error that parallel-wire length is more than a predetermined value.
(S23) The detected error is resolved by moving cells closely spaced less
than a predetermined interval apart and connected to the error-detected estimated
wires; the cell movement data is stored in a storage device; and such processes
are repeated N times; and the cell placement data is modified on the basis of the
cell movement data corresponding to the minimum value of error-count values of
all the N times. (S24) If the minimum value is not 0, (S25) a buffer
cell is inserted in the error-detected estimated wire. (S27) Obtained is
the wire density of estimated wiring having Manhattan-length path, and if the density
is more than a predetermined value, the design-target frame is enlarged in size,
and the process returns to the automatic cell placement process.