A method includes removing a first portion of a gate layer of a first transistor and leaving a second portion of the gate layer. The first transistor includes a drain region, a source region, and a gate stack, and the gate stack includes a gate dielectric layer, a gate conductive layer over the gate dielectric layer, and the gate layer directly on the gate conductive layer. The method includes removing a gate layer of a second transistor and forming a conductive region at a region previously occupied by the first portion of the gate layer of the first transistor, the unit resistance of the conductive region being less than that of the gate layer of the first transistor.