Patent Document ID: 8731893
Application ID: 13080154
Patent Flag: 1

Claim One:
1. A simulation method of simulating device characteristics of a transistor in which a source region and a drain region are isolated and formed in a silicon layer on a buried oxide film, and a gate electrode is formed on a gate insulating film on a channel region between the source region and the drain region, comprising the steps of: inputting a mathematical expression as one form of expression of data representing a characteristic of the transistor using an input device and causing a storage device to store the mathematical expression; inputting a device parameter for the transistor from the input device and causing the storage device to store the device parameter; calculating a first value of a surface potential of the silicon layer by performing computation using an arithmetic device based on the mathematical expression and the device parameter stored in the storage device; calculating a first value of a surface potential of a bulk layer under the buried oxide film when the silicon layer is in a partially depleted state and when the bulk layer is in a depleted state, calculating a second value of a surface potential of the bulk layer when the silicon layer is in the partially depleted state and when the hulk layer is in an inverted state, calculating a third value of a surface potential of the bulk layer when the silicon layer is in a fully depleted state and when the bulk layer is in the depleted state, and calculating a fourth value of a surface potential of the bulk layer when the silicon layer is in the fully depleted state and when the bulk layer is in the inverted state, by causing the arithmetic device to perform computation based on the mathematical expression and the device parameter stored in the storage device; causing the arithmetic device to perform computation based on the calculated first value of the surface potential of the silicon layer, at least one of the calculated first to fourth values of the surface potential of the bulk layer, and the mathematical expression stored in the storage device, and obtaining a fifth value of the surface potential of the bulk layer by iterative calculation; and calculating a first value of a lower surface potential of the silicon layer by causing the arithmetic device to perform computation based on the fifth value of the surface potential of the bulk layer obtained by the iterative calculation and the mathematical expression stored in the storage device.