A method and a device for estimating parameter variations of transistors that belong to the same circuit. The method includes: providing the first circuit; providing a test circuit adapted to perform a first function and a stacked test circuit adapted to perform a second function that substantially equals the first function; wherein the test circuit, the stacked test circuit and the first circuit are processed under substantially the same processing conditions; determining a relationship between a parameter of the test circuit and a parameter of the stacked test circuit; and estimating parameter variations of transistors that belong to the first circuit in response to the determined relationship.