PURPOSE: To boost a positive voltage as required and to enhance carrier transfer efficiency by forming a semiconductor region having such a conductive type as making the carrier as the minority carrier within the semiconductor region.

CONSTITUTION: The semiconductor regions 2 and 3 are charged respectively to the negative and positive potentials for the semiconductor region 1. The carrier 5 is implanted to the semiconductor 1 from the semiconductor region 2. The lattice or mesh P+ type semiconductor region 11 is formed as such a conductive type as making carrier as the minority carrier within the semiconductor region 1. The end part 7 of the depletion layer diffusing into the semiconductor region 2 from the P-N junction 6 is suppressed within the semiconductor region 11 even when a positive potential of the semiconductor region 3 for the semiconductor region 1 is kept high.