945,749. Semi-conductor devices. TEXAS INSTRUMENTS Inc. Feb. 2, 1960 [Feb. 6, 1959], No. 32744/63. Divided out of 945,734. Heading H1K. The subject matter of this Specification is included in Specification 945,734 from which the present Specification is divided but the claims relate to a device comprising a semi-conductor body with three superposed regions of alternate conductivity types forming a pair of PN junctions extending to a surface of the body and there defining two enclosed areas one within the other, with an insulating oxide of a semi-conductor covering selected parts of said surface, first and second ohmic contacts secured to said surface on opposite sides of the inner PN junction and a third ohmic contact secured to the third region. Specifications 945,737, 945,738, 945,739, 945,740, 945,741, 945,742, 945,743, 945,744, 945,745, 945,746, 945,747 and 945,748 also are referred to.