The invention provides a semiconductor device exhibiting a stable and high breakdown voltage, which is manufactured at a low manufacturing cost. The threaded portion presents a thread provided with a free helical edge extending along a substantially cylindrical surface and presents a substantially conical or frusto-conical core, and a thread provided at its free start with a cutting edge which is oriented with the same inclination as the thread and can reach the core center. An electrical contact protrudes outwardly from the inner surface and becomes nested with an electromagnetic pickup on the guitar.