A refresh time detection circuit and a semiconductor device including the same may be provided. The refresh time detection circuit may include a code generator configured to generate a code signal for detecting a refresh time. The refresh time detection circuit may include a latch circuit configured to generate a latch signal by latching the code signal according to a fail signal, and generate a pre-code signal and a post-code signal by latching each latch signal according to a pre-enable signal and a post-enable signal. The refresh time detection circuit may include a subtractor configured to output a refresh detection signal by performing subtraction between the pre-code signal and the post-code signal. The refresh time detection circuit may include a comparator configured to generate a detection signal by comparing the refresh detection signal with an offset signal based on the post-enable signal.

A refresh time detection circuit and a semiconductor device including the same may be provided. The refresh time detection circuit may include a code generator configured to generate a code signal for detecting a refresh time. The refresh time detection circuit may include a latch circuit configured to generate a latch signal by latching the code signal according to a fail signal, and generate a pre-code signal and a post-code signal by latching each latch signal according to a pre-enable signal and a post-enable signal. The refresh time detection circuit may include a subtractor configured to output a refresh detection signal by performing subtraction between the pre-code signal and the post-code signal. The refresh time detection circuit may include a comparator configured to generate a detection signal by comparing the refresh detection signal with an offset signal based on the post-enable signal.

A memory device with a novel structure that is suitable for a register file is provided. The memory device includes a first memory circuit and a second memory circuit. The first memory circuit includes a first logic element and a second logic element each of which is configured to perform logic inversion, a selection circuit, a first switch, a second switch, and a third switch. The second memory circuit includes a first transistor in which a channel formation region is provided in an oxide semiconductor film, a second transistor, and a capacitor to which a potential is supplied through the first transistor.

A memory device with a novel structure that is suitable for a register file is provided. The memory device includes a first memory circuit and a second memory circuit. The first memory circuit includes a first logic element and a second logic element each of which is configured to perform logic inversion, a selection circuit, a first switch, a second switch, and a third switch. The second memory circuit includes a first transistor in which a channel formation region is provided in an oxide semiconductor film, a second transistor, and a capacitor to which a potential is supplied through the first transistor.

A semiconductor device capable of high speed operation is provided. Further, a semiconductor device in which change in electric characteristics due to a short channel effect is hardly caused is provided. An oxide semiconductor having crystallinity is used for a semiconductor layer of a transistor. A channel formation region, a source region, and a drain region are formed in the semiconductor layer. The source region and the drain region are formed by self-aligned process in which one or more elements selected from Group 15 elements are added to the semiconductor layer with the use of a gate electrode as a mask. The source region and the drain region can have a wurtzite crystal structure.

A semiconductor device capable of high speed operation is provided. Further, a semiconductor device in which change in electric characteristics due to a short channel effect is hardly caused is provided. An oxide semiconductor having crystallinity is used for a semiconductor layer of a transistor. A channel formation region, a source region, and a drain region are formed in the semiconductor layer. The source region and the drain region are formed by self-aligned process in which one or more elements selected from Group 15 elements are added to the semiconductor layer with the use of a gate electrode as a mask. The source region and the drain region can have a wurtzite crystal structure.

In a configuration including a memory cell that retains multilevel data by controlling the on/off state of a transistor, correct data can be read out even if a potential of data retained by turning off the transistor is changed. The memory cell controls writing or retention of data corresponding to one of a plurality of potentials by controlling an on/off state of the transistor. The write voltage generator circuit outputs a first write voltage of data to be written to the memory cell. The write voltage generator circuit obtains a read voltage of the data by reading the first write voltage written to the memory cell. The write voltage generator circuit generates a second write voltage by correcting a change of the first write voltage caused by turning off the transistor, and outputs the second write voltage to the memory cell.

In a configuration including a memory cell that retains multilevel data by controlling the on/off state of a transistor, correct data can be read out even if a potential of data retained by turning off the transistor is changed. The memory cell controls writing or retention of data corresponding to one of a plurality of potentials by controlling an on/off state of the transistor. The write voltage generator circuit outputs a first write voltage of data to be written to the memory cell. The write voltage generator circuit obtains a read voltage of the data by reading the first write voltage written to the memory cell. The write voltage generator circuit generates a second write voltage by correcting a change of the first write voltage caused by turning off the transistor, and outputs the second write voltage to the memory cell.

A semiconductor device with a large storage capacity per unit area is provided.

A semiconductor device includes a memory cell. The memory cell includes a first conductor; a first insulator over the first conductor; a first oxide over the first insulator and including a first region, a second region, and a third region positioned between the first region and the second region; a second insulator over the first oxide; a second conductor over the second insulator; a third insulator positioned in contact with a side surface of the first region; and a second oxide positioned on the side surface of the first region, with the third insulator therebetween. The first region includes a region overlapping the first conductor. The third region includes a region overlapped by the second conductor. The first region and the second region have a lower resistance than the third region.

A semiconductor device with a large storage capacity per unit area is provided.

A semiconductor device includes a memory cell. The memory cell includes a first conductor; a first insulator over the first conductor; a first oxide over the first insulator and including a first region, a second region, and a third region positioned between the first region and the second region; a second insulator over the first oxide; a second conductor over the second insulator; a third insulator positioned in contact with a side surface of the first region; and a second oxide positioned on the side surface of the first region, with the third insulator therebetween. The first region includes a region overlapping the first conductor. The third region includes a region overlapped by the second conductor. The first region and the second region have a lower resistance than the third region.