A method of generating an ion implantation distribution by a computer is disclosed. The method includes calculating ion implantation distribution regions in a case of generating the ion implantation distribution with a large tilt angle and generating an analytical model of the ion implantation distribution in correspondence with each of the ion implantation distribution regions by using a Gauss distribution model, in which the ion implantation distribution regions have different influence on a channel region depending on a gate structure formed on the ion distribution regions.