1. A simulator for a chemical mechanical polishing process for planarizing a semiconductor substrate, said simulator receiving: a pattern density data containing information about a pattern density per unit region of a fabrication pattern in a pattern forming process of a semiconductor device; and first and second measured data about height distributions of irregularities on said semiconductor substrate that are measured before and after a chemical mechanical polishing process executed with respect to said pattern forming process, wherein said first measured data is compared with a first calculated data about a two-dimensional distribution of irregularities on said semiconductor substrate before said chemical mechanical polishing process which is calculated from said pattern density data, a least squares analysis is performed to obtain a first correlation coefficient, and a parameter fitting is performed such that square of said first correlation coefficient becomes a maximum, and said second measured data is compared with a second calculation data about a two-dimensional distribution of irregularities on said semiconductor substrate after said chemical mechanical polishing process which is calculated from said pattern density data, a least squares analysis is performed to obtain a second correlation coefficient, and a parameter fitting is performed such that square of said second correlation coefficient becomes a maximum.