Read-only memory and method for fabricating the same
AssigneeOki Electric Industry Co., Ltd.
InventorsHiroshi Mizuhashi, Teruo Katoh
Life of this patent
Estimating the term…
Abstract
A read-only memory includes a semiconductor substrate; a memory cell matrix which is formed on the semiconductor substrate; and word and bit lines which define the locations of the memory cell matrix. The memory cell matrix includes field effect transistors, each of which turns off when accessed or addressed; and conducting regions, which keep conductive state all the time. Binary data stored in the memory cell matrix are determined by detecting current flowing through the selected bit line.
Claims26
A read-only memory, comprising:
- a semiconductor substrate;
- a memory cell matrix which is formed on the semiconductor substrate;
- and
- word and bit lines which define the locations of the memory cell matrix, wherein
- the memory cell matrix comprises field effect transistors, each of which turns off when accessed or addressed;
- and conducting regions which keep conductive state all the time;
- and
- binary data stored in the memory cell matrix are determined by detecting current flowing through the corresponding bit line.
A mask ROM, comprising:
- a semiconductor substrate;
- a memory cell matrix which is formed on the semiconductor substrate;
- and is comprising field effect transistors, each of which turns off when accessed or addressed, and conducting regions which keep conductive state all the time;
- and
- word and bit lines which define the locations of the memory cell matrix, wherein
- the field effect transistors, forming the memory cell matrix, are enhancement type field effect transistors, in which sources and drains are formed by an ion implantation process to the semiconductor substrate;
- the conducting regions are formed by an ion implantation process to specific regions in the semiconductor substrate at the same time when the sources and drains of the field effect transistors are formed;
- and
- binary data stored in the memory cell matrix are determined by detecting current flowing through the corresponding bit line.
A method for fabricating a read-only memory, comprising the steps of:
- providing a semiconductor substrate;
- forming active regions extending in a first direction to define memory cell lines along bit lines;
- forming a gate oxide layer on the active regions;
- forming a gate layer on the gate oxide layer;
- removing a part of the gate layer except areas for gates of field effect transistors, which store one type of binary data;
- forming impurity regions at both sides of each gate of the field effect transistor to form source and drain thereof;
- implanting impurities in the semiconductor substrate using the gate as a mask to form conducting regions, which store the other type of binary data therein;
- forming an insulating layer over the gates of the field effect transistors;
- forming contact holes passing through the interlayer insulating layer;
- and
- forming a wiring pattern which is connected to the gates via the contact holes and to word lines, which are extending in a second direction orthogonal to the first direction, wherein
- the word and bit lines define the locations of the memory cell matrix;
- and
- binary data stored in the memory cell matrix are decided by detecting current flowing through the corresponding bit line.
Dependencies are inferred from the claim text.