A method includes forming a first device die and a second device die. The first device die includes a first integrated circuit, and a first bond pad at a first surface of the first device die. The first integrated circuit is electrically connected to the first bond pad. The second device die includes a power switch that includes a first source/drain region, a second source/drain region, a second bond pad electrically connecting to the first source/drain region, and a third bond pad electrically connecting to the second source/drain region. The method further includes bonding the first device die with the second device die to form a package, with the first bond pad bonding to the third bond pad, and bonding the package to a package component.