An integrated circuit includes gate-all-around (GAA) nanowire transistors, GAA nanosheet transistors, and planar devices on the same substrate. Gate dielectric layers of the GAA nanowire transistors and the GAA nanosheet transistors have substantially the same thickness which is smaller than the thickness of the gate dielectric layer of the planar devices. The channel width of the planar devices is greater than the channel width of the GAA nanosheet transistors, which is greater than the channel width of the GAA nanowire transistors.