Of a plurality of standard cells in which an N-well region and a P-well region are vertically formed, some standard cells have a border line between the N-well region and the P-well region which is set to be a low height (first height), and other standard cells have a border line between the N-well region and the P-well region which is set to be a high height (second height), depending on the size of a transistor formed in the standard cell. Although these standard cells have different border lines, a standard cell for linking the border lines is provided. In such a standard cell, an empty space is created by forming a small-size transistor therein, and the empty space is utilized so that, for example, a left end of the border line is set to have the first height and a right end of the border line is set to have the second height, whereby the border line is converted so as to link the heights therein.