Nec Corporation

Hitachi-kokusai Electric Inc.

Satoru Tagami

Jun Kawai

Akira Fukuoka

Takayuki Inoi

Yasuhiro Inokuchi

Hiromi Suzuki

Sadayuki Takahashi

Masako Inagawa

Masayuki Tsuneda

Koichi Morimoto

Tsuyoshi Kitami

Koichi Zama

Ryoichi Furukawa

Tadanori Yoshida

A manufacturing method for a semiconductor device, including forming on or above a semiconductor substrate a silicon film a surface of which has a first polycrystalline silicon film with mushroom or hemisphere-shaped crystal grains, and forming a Ta O film on the silicon film at a pressure of 40 Pa or lower and at a temperature of 480&deg; C. or lower, using a gas obtained by vaporizing Ta(OC H ) as a tantalum source gas.

Manufacturing method for semiconductor device

A piezoelectric transformer includes strip form electrodes on opposing upper and lower surfaces of a piezoelectric ceramic plate formed by screen printing using a conductive paste. By using strip form electrodes, discharge of a driving portion during polarization, degradation of reliability of mechanical strength due to excessive stress in a power generating portion during polarization, and instability of transformer output due to breakage of the electrode is prevented.

Piezoelectric transformer

A piezoelectric actuator is driven by continuously applying a pulse voltage or an AC voltage to a piezoelectric element, so as to cause the piezoelectric element to generate heat because of a dielectric loss of the piezoelectric element itself. If the temperature of the piezoelectric element reaches a temperature not less than 15.degree. C., moisture contained in atmosphere is effectively prevented from entering into a resin casing of the piezoelectric actuator enclosing therein the piezoelectric element. Otherwise, moisture condensation or sweating would occur on a surface of the piezoelectric element. Therefore, even if the piezoelectric actuator is used in atmosphere of high humidity, a discharge breakdown will not occur, and reliability is remarkably increased.

Method for driving piezoelectric actuator

A long thin rectangular body of piezoelectric material is divided, in the longitudinal direction thereof, into a plurality of regions which include at least one driving region and at least one driven region. The driven region includes two electrodes which are formed such as to respectively cover opposite side surfaces of the driven region in a plane parallel to the longitudinal direction and to respectively extend inwardly in a transverse direction of the body by a predetermined amount over two major surfaces of the driven region. The driven region is polarized in a lateral direction of the body. As an alternative, the driven region is provided with two electrodes each of which consists of a pair of relatively narrow strip-like portions. The strip-like portions of one electrode extend over the two major surfaces adjacent to one edge of the driven region in the longitudinal direction of the body. The strip-like portions of the other electrode are similarly provided at the opposite side of the driven region. The driven region is polarized in a direction perpendicular to the longitudinal direction of the body.

Piezoelectric transformer having improved electrode arrangement

A long relatively thin rectangular body of piezoelectric material is divided into driving and driven regions in a longitudinal direction thereof. Two electrodes are applied respectively to two major surfaces of the driving region which is polarized in a thickness direction of the driving region. Another two electrodes are formed on one major surface of the driven region. Each of the two electrodes applied to the driven region has a plurality of finger-like portions which extend in the longitudinal direction. The finger-like portions of formed on the driven region are arranged in an interdigital manner. The driven region has a plurality of regions which are defined by adjacent finger-like portions and which are polarized in a direction perpendicular to the longitudinal direction.

A piezoelectric transformer is constituted of a piezoelectric plate in the form of an elongated plate and electrodes formed thereon. A pair of driver sections and a generator section are formed in two opposite end regions of the piezoelectric plate containing a mechanical resonance node and in a central region of the piezoelectric plate containing a mechanical resonance node, respectively, in an oscillation mode of three times of 1/2 of the resonance wavelength .lambda. of the longitudinal mechanical oscillation in length of the piezoelectric plate. The driver sections are polarized in a thickness direction but in directions opposite to each other. The driver sections have a distance of .lambda./2 from the corresponding end of the piezoelectric plate.

Growing community of inventors

Tokyo, Japan

Satoru Tagami