To provide a high-frequency power MOSFET together with its manufacturing method, in which source grounding is made with no bonding wire by forming a source electrode on the rear surface, by reducing the ground inductance as well as a feed-back capacitance, output capacitance, and input capacitance, resulting in improved high-frequency characteristics.

A vertical field-effect transistor is provided where the source electrode 22 is formed on the rear surface of a first conductivity substrate 11. A second conductivity base layer 12 and a second base layer 13 are sequentially formed on the first conductivity substrate 11, and a groove extending from the surface of the second base layer 13 to the substrate 11 is formed. The gate electrode 23 is formed on the lower part of the groove through an insulating film, and an insulator is packed above and below the gate electrode 23 in the groove. A drift region 14 and a source diffusion region 111 are formed on the side surface of the groove by self-matching manner to the gate electrode. The drain region 15 is formed on the surface of the second base layer.