High performance stacked LDD RF LDMOSFET

A novel silicon RF LDMOSFET structure, using a simple yet effective concept of stacked LDD, is proposed. The stacked layers of LDD minimises the on-state resistance of the transistor due to the n⁺ doping used in the top LDD layer, and also raises the device breakdown voltage due to the charge compensation in the composite LDD region. Therefore, for the same blocking voltage rating, the stacked LDD structure allows the LDMOSFET to have a higher current handling capability. This in turn causes the transconductance Gm to be higher, leading to higher RF performance for the power device