Substrate identification circuit and semiconductor device

摘要

Provided is a substrate identification circuit that generates a numeric value, whose duplication is difficult and which is proper to a substrate, at low cost and a semiconductor device having such a substrate identification circuit. A substrate identification circuit 304 is produced by utilizing variations in characteristics among TFTs formed on a substrate having an insulating surface. The substrate identification circuit 304 includes a plurality of proper bit generating circuits, each of which is constructed from a plurality of TFTs and outputs a one-bit random number based on variations in characteristics among the plurality of TFTs. The substrate identification circuit generates a numeric value proper to the substrate using the one-bit random number. The substrate identification circuit may include a circuit that makes a judgment by comparing the numeric value proper to the substrate with an identification number inputted from the outside.