A neural interface device, which comprises: a) a carrier comprising: (i) a carrier sidewall having a first length extending from a proximal carrier end to a distal carrier portion having a distal carrier end; (ii) wherein the carrier sidewall extends to spaced-apart first and second surfaces (102E, 102F) and has a width extending from a third carrier edge to an opposed fourth carrier edge, the first and second carrier surfaces (102E, 102F) meeting the proximal and distal carrier ends (102A, 102B) and the third and fourth carrier edges (102C, 102D; (iii) wherein the carrier has a first thickness between the first and second carrier surfaces (102E, 102F) and wherein the distal carrier portion has a step transition to a thinner carrier sidewall portion having a second thickness less than the first thickness; b) a substrate supported on the thinner carrier sidewall portion; c) at least one electrode supported on the substrate, wherein the electrode is configured for at least one of electrical stimulation of body tissue and sensing of physiological characteristics of the body tissue; wherein the step transition has a height that substantially matches the thickness of the substrate comprising the electrode to provide a smooth transition from the carrier sidewall to the substrate; d) an electrical conductor that extends from the proximal carrier end to the thinner carrier sidewall portion, where it electrically connects the at least one electrode, wherein the proximal carrier end is electrically connectable to a medical device; and e) at least one deformable segment of the carrier sidewall intermediate the proximal carrier end and the distal carrier end, wherein the deformable segment comprises at least one slit extending completely through the first thickness, and wherein the at least one slit provides an open space having a slit length extending from a proximal slit end spaced distally from the proximal carrier end to a distal slit end spaced proximally from the distal carrier end to thereby provide first and second strand portions of the carrier sidewall, the first and second strand portions being intermediate the proximal and distal carrier ends (102A, 102B) and the third and fourth carrier edges (102C, 102D). a) a carrier comprising: (i) a carrier sidewall having a first length extending from a proximal carrier end to a distal carrier portion having a distal carrier end; (ii) wherein the carrier sidewall extends to spaced-apart first and second surfaces (102E, 102F) and has a width extending from a third carrier edge to an opposed fourth carrier edge, the first and second carrier surfaces (102E, 102F) meeting the proximal and distal carrier ends (102A, 102B) and the third and fourth carrier edges (102C, 102D; (iii) wherein the carrier has a first thickness between the first and second carrier surfaces (102E, 102F) and wherein the distal carrier portion has a step transition to a thinner carrier sidewall portion having a second thickness less than the first thickness; (i) a carrier sidewall having a first length extending from a proximal carrier end to a distal carrier portion having a distal carrier end; (ii) wherein the carrier sidewall extends to spaced-apart first and second surfaces (102E, 102F) and has a width extending from a third carrier edge to an opposed fourth carrier edge, the first and second carrier surfaces (102E, 102F) meeting the proximal and distal carrier ends (102A, 102B) and the third and fourth carrier edges (102C, 102D; (iii) wherein the carrier has a first thickness between the first and second carrier surfaces (102E, 102F) and wherein the distal carrier portion has a step transition to a thinner carrier sidewall portion having a second thickness less than the first thickness; b) a substrate supported on the thinner carrier sidewall portion; c) at least one electrode supported on the substrate, wherein the electrode is configured for at least one of electrical stimulation of body tissue and sensing of physiological characteristics of the body tissue; wherein the step transition has a height that substantially matches the thickness of the substrate comprising the electrode to provide a smooth transition from the carrier sidewall to the substrate; d) an electrical conductor that extends from the proximal carrier end to the thinner carrier sidewall portion, where it electrically connects the at least one electrode, wherein the proximal carrier end is electrically connectable to a medical device; and e) at least one deformable segment of the carrier sidewall intermediate the proximal carrier end and the distal carrier end, wherein the deformable segment comprises at least one slit extending completely through the first thickness, and wherein the at least one slit provides an open space having a slit length extending from a proximal slit end spaced distally from the proximal carrier end to a distal slit end spaced proximally from the distal carrier end to thereby provide first and second strand portions of the carrier sidewall, the first and second strand portions being intermediate the proximal and distal carrier ends (102A, 102B) and the third and fourth carrier edges (102C, 102D).