A method for producing a layout of a device in an integrated circuit before actually fabricated is provided. The method includes inputting at least one fixed parameter for the device for fabrication. And then, a first part of a set of variable parameters of a layout of the device is input. The complete set of the variable parameters is generated. It is checked whether or not the layout with the parameters is satisfying a requirement, wherein an end step is reached if the layout is accepted by the requirement, and a new part of the set of variable parameters as the first part being looping in the foregoing steps if the layout is not accepted by the requirement.