Abstract: A semiconductor device having active parts made from semiconductor diamond. The active parts include a high doped diamond layer for supplying free carriers and a non- or low doped diamond layer for giving the free carriers a conductive region. The free carriers are transferred from the high doped diamond layer to the non- or low doped diamond layer by diffusion or an applied electric field. Since the free carriers move at high speeds in the non- or low doped diamond layer without being scattered by dopant atoms, the semiconductor device is applicable to high frequency devices with stability against a change in temperature.

Abstract: Improvement of a high frequency device having metal layers, active semiconductor layers and other semiconductor layers which make use of carrier avalanche or carrier injection induced by a reverse bias voltage for amplification or oscillation of high frequency waves. The active semiconductor layers are made of semiconductor diamond. High heat conductivity and high insulation breakdown voltage of diamond heighten the output power of oscillation or amplification.

Abstract: A method of and an apparatus for vapor-phase synthesizing a hard material use a raw material gas supplied into a reaction tube (6) while irradiating a region of the reaction tube (6) with microwaves (18) of a prescribed frequency for causing a synthesizing reaction to produce the hard material along a prescribed direction, by a plasma generation. In the reaction tube (6), at least two plate electrodes (17a, 17b, 19a, 19b) are oppositely arranged in parallel vertically to electric fields of the microwaves (18), so that the plasma is excited between the plate electrodes (17a, 17b, 19a, 19b) for vapor-phase synthesizing the hard material. The microwaves (18) of high electric power are introduced into the reaction tube (6) through a waveguide (5) without loss, so that strong electric fields can be homogeneously and stably distributed between the opposite plate electrodes.

Abstract: A Hall device having an active part made from semiconductor diamond. The Hall device works even at high temperature or in corrosive atmosphere. Boron doped diamond is suitable for controlling the acceptor concentration.

Abstract: Doping a dopant into a diamond semiconductor causes lattice defects. The pn junction diode or the Schottky junction diode made from diamond has low break down voltage and high reverse leakage current owing to the lattice defects. A non-doped or low doped diamond layer with high resistivity is epitaxially grown between the N-type diamond layer and the p-type diamond layer in the pn junction diode or between the metal layer and the doped diamond layer in the Schottky diode. The intermediate layer heightens the break down voltage and decreases the reverse leakage current.

Abstract: A schottky contact which comprises a single crystal diamond substrate, an epitaxial diamond layer formed on said substrate and a schottky electrode layer formed on said epitaxial diamond layer, wherein said substrate has at least one polished surface which inclines at an angle of not larger than 10.degree. to a (100) plane and said epitaxial diamond layer is formed on said surface, provides a device which has good thermal resistance and environmental resistance and which device can be easily highly integrated.