Semiconductor device having level shift diode

Claim 2

A semiconductor device comprising a substrate (31-33); at least one field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22) provided on said substrate; and at least one level shift diode (D1-D4) provided on said substrate, characterized in that said level shift diode (D1-D4) comprises a first layer (12, 34B, 54b, 62a, 62c, 74b, 82a, 82c) made of a first compound semiconductor and a second layer (13, 34C, 61a, 61c, 63a, 63c, 81a, 81c, 83a, 83c) made of a second compound semiconductor having an electron affinity smaller than that of the first compound semiconductor, said first and second layers forming a heterojunction therebetween, said first and second compound semiconductors being both made of either one of n-type and i-type semiconductors, said first layer being used in common with said field effect transistor as a layer (34, 34A, 54, 74) of said field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22).

Claim 3

A semiconductor device as claimed in claim 1, characterized in that a composition of said second compound semiconductor is selected so that said level shift diode has a predetermined level shift quantity.

Claim 4

A semiconductor device as claimed in claim 1 or 2, characterized in that a plurality of said first and second layers are provided on said substrate to constitute a plurality of level shift diodes (D1-D4).

Claim 5

A semiconductor device as claimed in claim 3, characterized in that said first and second layers are stacked alternately thereby forming said plurality of level shift diodes which are connected in series.

Claim 6

A semiconductor device as claimed in claim 3, characterized in that said first and second layers are stacked alternately at a plurality of isolated locations on said substrate, one location having a number of said first and second layers different from that at another location so that level shift diodes formed at said one and other locations are connected in mutually opposite directions.

Claim 7

A semiconductor device as claimed in claim 5, characterized in that a sequence in which said first and second layers are stacked is the same at all of said locations on said substrate.

Claim 8

A semiconductor device as claimed in any of claims 1 to 6, characterized in that said field effect transistor is a high electron mobility transistor.

Claim 9

A semiconductor device as claimed in any of claims 1 to 7, characterized in that said first compound semiconductor is gallium arsenide (GaAs) and said second compound semiconductor is aluminum gallium arsenide (AlGaAs).

Claim 10

A semiconductor device as claimed in any of claims 1 to 7, characterized in that said first compound semiconductor is gallium arsenide (GaAs) and said second compound semiconductor is aluminum gallium arsenide Al x Ga 1-x As, said level shift diode having a level shift quantity determined by Al content x.

Claim 11

A semiconductor device comprising a substrate (31-33); at least one field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22) provided on said substrate; and at least one level shift diode (D1-D4) provided on said substrate, characterized in that said level shift diode (D1-D4) comprises a first layer (12, 34B, 54b, 62a, 62c, 74b, 82a, 82c) made of a first compound semiconductor and a second layer (13, 34C, 61a, 61c, 63a, 63c, 81a, 81c, 83a, 83c) made of a second compound semiconductor having an electron affinity smaller than that of the first compound semiconductor, said first and second layers forming a heterojunction therebetween, said first compound semiconductor having a first energy level of the bottom of the valence band, said second compound semiconductor having a second energy level of the bottom of the valence band being lower for a hole than the first energy level at the heterojunction, said first and second compound semiconductors being both made of either one of p-type and i-type semiconductors, said first layer being used in common with said field effect transistor as a layer (34, 34A, 54, 74) of said field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22).

Claim 12

A semiconductor device comprising a substrate (31-33); at least one field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22) provided on said substrate; and at least one level shift diode (D1-D4) provided on said substrate, characterized in that said level shift diode (D1-D4) comprises a first layer (12, 34B, 54b, 62a, 62c, 74b, 82a, 82c) made of a first compound semiconductor and a second layer (13, 34C, 61a, 61c, 63a, 63c, 81a, 81c, 83a, 83c) made of a second compound semiconductor having an electron affinity smaller than that of the first compound semiconductor, said first and second layers forming a heterojunction therebetween, said first compound semiconductor having a first energy level of the bottom of the valence band, said second compound semiconductor having a second energy level of the bottom of the valence band being lower for a hole than the first energy level at the heterojunction, said first and second compound semiconductors being both made of either one of p-type and i-type semiconductors, said first layer being used in common with said field effect transistor as a layer (34, 34A, 54, 74) of said field effect transistor (Q3, Q4, Q11, Q12, Q13, Q22).

Claim 13

A semiconductor device as claimed in claim 10, characterized in that a composition of said second compound semiconductor is selected so that said level shift diode has a predetermined level shift quantity.

Claim 14

A semiconductor device as claimed in claim 10 or 11, characterized in that a plurality of said first and second layers are provided on said substrate to constitute a plurality of level shift diodes.

Claim 15

A semiconductor device as claimed in claim 12, characterized in that said first and second layers are stacked alternately thereby forming said plurality of level shift diodes which are connected in series.

Claim 16

A semiconductor device as claimed in claim 12, characterized in that said first and second layers are stacked alternately at a plurality of isolated locations on said substrate, one location having a number of said first and second layers different from that at another location so that level shift diodes formed at said one and other locations are connected in mutually opposite directions.

Claim 17

A semiconductor device as claimed in claim 14, characterized in that a sequence in which said first and second layers are stacked is the same at all of said locations on said substrate.

Claim 18

A semiconductor device as claimed in any of claims 10 to 15, characterized in that said field effect transistor is a high electron mobility transistor.