Disclosed herein are an asymmetrical multilayer substrate, an RF module, and a method for manufacturing the asymmetrical multilayer substrate. The asymmetrical multilayer substrate includes a core layer, a first pattern layer formed on one side of the core layer and including a first signal line pattern, a second pattern layer formed on the other side and including a second metal plate and a second routing line pattern, a first insulating layer thinner than the core layer formed on the second pattern layer and including a first via, and a third pattern layer formed on the first insulating layer and including a third signal line pattern, wherein an impedance transformation circuit including an impedance load and a parasitic capacitance load on the transmission line is formed for impedance matching in signal transmission between the signal line patterns formed in the upper and lower side directions of the core layer.