JPH04109663A - Semiconductor device - Google Patents

Abstract

PURPOSE:To eliminate a substrate current and to efficiently step up a voltage by forming a transistor of a booster on an SOI substrate. CONSTITUTION:In a semiconductor device having a booster in combination of a transistor and a capacitor, the transistor is formed on an SOI substrate. That is, transistors are formed on the substrate to be completely insulated by the substrate and other transistors, an oxide film 2. Thus, since the substrate current can be eliminated, a voltage can be efficiently increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device having a booster circuit, such as a low voltage single power supply EEPROM.

[Summary of the invention]

The present invention provides a semiconductor device having a booster circuit, in which So.
By forming the transistors of the booster circuit on the l substrate, there is no substrate current and it is possible to efficiently boost the voltage to more than ten times the external input voltage.

[Conventional technology]

A transistor formed on a silicon substrate as shown in FIG. 3 has been used, for example, in a booster circuit as shown in FIG. Therefore, the capacitors 01 to CN are connected in order. By sequentially applying the voltage from the outside to 1-N, the electric charge stored in each capacitor is used to convert ■1 to VN (
V+ <Vz...>VN), the voltage was increased in order to obtain a high voltage.

[Problem to be solved by the invention]

Because of the presence of substrate current, the boost efficiency deteriorates as it approaches ■8, for example, ■. = about 1.5M, 20(
It was difficult to obtain a voltage of V).

[Means to solve the problem]

In order to solve the above problems, the present invention forms each transistor on a Sol structure so that it is completely insulated from the substrate and other transistors by an oxide film.

[Effect]

As described above, by completely insulating each transistor from the substrate and other transistors, the substrate current can be eliminated, so that the voltage can be increased efficiently.

〔Example〕

As shown in FIG. 1, a booster circuit transistor is formed on a Sol substrate. For example, LOCO3 is used for element isolation method.
When this method is used, a transistor with a cross-sectional shape as shown in FIG. 1 is obtained. Then, it becomes completely electrically isolated from the substrate. Therefore, for example, if it is incorporated into a circuit as shown in Figure 2 and boosted, the substrate current will disappear, so
Efficient boosting can be performed.

〔Effect of the invention〕

As explained above, by forming a booster circuit on an S0I substrate, the efficiency of boosting can be increased. It becomes possible to reduce the number of capacitors and transistors.

FIG. 1 is a sectional view of a transistor used in an embodiment of the present invention, FIG. 2 is a circuit diagram showing a circuit of an embodiment of the invention, and FIG. 3 is a sectional view of a conventionally used transistor.

silicon substrate Oxide film Element M oxide film gate wiring silicon that's all Applicant: Seiko Electronics Industries Co., Ltd. Agent: Patent Attorney Takayoshi Hayashi

[Brief explanation of drawings]

Typical circuit diagram of booster circuit 210th

Claims (1)

[Claims] 1. A semiconductor device having a booster circuit that combines a transistor and a capacitor, wherein the transistor is formed on an SOI substrate.