Patent ID: 6867107

Claim:
A process for manufacturing a variable capacitance device comprising the steps of; forming a first region in a semiconductor layer formed on a substrate via an insulating layer, the first region containing a first conductivity type dopant; forming a second region in a portion of the first region, the second region containing a second conductivity type dopant at a higher dopant concentration than that of the first region; and forming a third region in a portion of the first region and apart from the second region, the third region containing a first conductivity type dopant at a higher dopant concentration than that of the first region, the contact area between the third region and the first region being smaller than that between the first region and the second region, wherein the process further comprises the steps of: forming, prior to the formation of the first region, a device isolation region in the semiconductor layer, the device isolation region isolating a first semiconductor-device-forming section for forming the variable capacitance device from each of a second semiconductor-device-forming section and a third semiconductor-device-forming section; forming, in the step of forming the first region, a fourth region in the second semiconductor-device-forming section, the fourth region containing the same conductivity type dopant as the first region; forming a fifth region in the third semiconductor-device-forming section, the fifth region containing a second conductivity type dopant at a lower dopant concentration than that of the second region; forming a gate electrode on each of the fourth and fifth regions; forming, in the step of forming the second region, a sixth region in the fourth region by using the gate electrode as a mask, the sixth region containing the same conductivity type dopant as the second region; and forming, in the step of forming the third region, a seventh region in the fifth region by using the gate electrode as a mask, the seventh region containing the same conductivity type dopant as the third region.